Reference:Movements: Difference between revisions

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{{#seo:
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|title=Rolex Movements & Calibers — Cross-Family Reference | BezelBase
|title=Rolex Movements & Calibers — Cross-Family Reference | BezelBase
|description=Cross-family caliber catalogue for vintage and discontinued Rolex. Every movement that powered a pre-2020 Daytona, Submariner, GMT-Master, Explorer, or Oyster Perpetual reference, with deep per-caliber technical and visual detail.
|description=Cross-family caliber catalogue for vintage and discontinued Rolex watches, covering the movements used in pre-2020 Daytona, Submariner, GMT-Master, Explorer, and Oyster Perpetual references.
|keywords=Rolex caliber, Rolex movement, cal 4030, cal 4130, cal 727, Valjoux 72, Zenith El Primero, cal 1570, cal 1575, cal 3035, cal 3135, cal 3185, cal 3186, Oysterquartz 5035, Rolex chronograph caliber, vintage Rolex movement
|keywords=Rolex caliber, Rolex movement, cal 4030, cal 4130, cal 727, Valjoux 72, Zenith El Primero, cal 1570, cal 1575, cal 3035, cal 3135, cal 3185, cal 3186, Oysterquartz 5035, Rolex chronograph caliber, vintage Rolex movement
|type=Article
|type=Article
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== Rolex movements ==
== Rolex movements ==


Every caliber below powered a reference documented on this wiki. Each gets its own entry: specification woven into the history rather than boxed off in a table, the visual and finishing details that let a collector recognize a genuine example, and a photograph where one has been sourced and verified. Fitment is kept to a representative reference or two rather than an exhaustive list — the individual [[Reference:oyster-perpetual|reference]] pages carry the full case-by-case detail.
The entries cover calibers tied to the Rolex families documented on this wiki, including a few poorly documented numbers with no confirmed fitment. Specifications sit alongside the history, visual details, and known reference uses. Individual reference pages carry the case-by-case fitment detail.


The caliber number is engraved on the movement itself and read with the caseback off; it is separate from the case serial, which is the number that dates the watch on the [[Reference:Serial-numbers|serial-number page]]. Where a movement number and case number diverge sharply, as on the stockpiled Prince calibers, the movement was made well before the case it sits in.
The caliber number is engraved on the movement itself and read with the caseback off; it is separate from the case serial, which is the number that dates the watch on the [[Reference:Serial-numbers|serial-number page]]. Where a movement number and case number diverge sharply, as on the stockpiled Prince calibers, the movement was made well before the case it sits in.


Nearly every mechanical Rolex movement on this page, from the earliest Prince calibers through the modern in-house automatics, was physically manufactured by Aegler in Bienne — Rolex's own supplier and, from 2004, its own subsidiary. Two component technologies recur across dozens of the calibers below and are worth understanding once rather than re-explained each time. Glucydur balances, standard on Rolex automatics from the 1930s onward, are a beryllium-bronze alloy — the name fuses "glucinium" (an old name for beryllium) with "dur" for hard — chosen because the alloy resists magnetism and temperature-driven rate variation far better than the steel balances it replaced. Kif shock protection, from the Vallée de Joux firm founded in 1944, cushions the balance staff pivots against impact with a spring-loaded free-bearing jewel setting; Rolex's "Kif Ultraflex" and "Kif Elastor" are Rolex-specific tunings of the same underlying system, not distinct technologies. Parachrom is Rolex's own invention: a niobium-zirconium-oxygen hairspring alloy the company designed and manufactures in-house, introduced from 2000 and distinguished by its blue oxide coating from around 2005, roughly ten times more resistant to shock and largely immune to magnetic fields and temperature swings compared to the Nivarox alloys it replaced.
Aegler in Bienne made most of the mechanical movements covered here. The firm supplied Rolex as an independent manufacturer before becoming its subsidiary in 2004; this manufacturing relationship is separate from whether a caliber used an outside design, as the Valjoux- and Zenith-based chronographs did.
 
Several component technologies recur across the range. Glucydur balances, standard on Rolex automatics from the 1930s onward, use a beryllium-bronze alloy that resists magnetism and temperature-driven rate variation better than the steel balances it replaced. The name combines "glucinium," an old name for beryllium, with "dur," meaning hard. Kif shock protection, made by the Vallée de Joux firm founded in 1944, cushions the balance-staff pivots with a spring-loaded free-bearing jewel setting. Rolex's "Kif Ultraflex" and "Kif Elastor" are its versions of that system rather than separate technologies. Introduced in 2000, Parachrom is Rolex's niobium-zirconium-oxygen hairspring alloy. A blue oxide coating distinguished it from around 2005; Rolex rates it as about ten times more resistant to shock than the Nivarox alloys it replaced, as well as largely immune to magnetism and temperature changes.
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== Prince (shaped movements) ==
== Prince (shaped movements) ==


The Prince family runs on Aegler shaped movements, older than every other Rolex caliber on this page. Wilsdorf and Aegler patented the layout in 1927: a "shaped watch movement with a seconds dial" that put the winding barrel at one end of the rectangular movement and the balance at the other. That separation is why Prince movements could carry a larger balance wheel than rival shaped calibers of the period, and a bigger mainspring barrel too — better precision, longer reserve, both from the same design choice.
The Prince family uses Aegler shaped movements, older than every other Rolex caliber on this page. Wilsdorf and Aegler patented the layout in 1927 as a "shaped watch movement with a seconds dial." It placed the winding barrel at one end of the rectangular movement and the balance at the other, leaving room for a larger balance wheel and mainspring barrel than rival shaped calibers of the period. The result was better precision and a longer reserve.


Aegler made these movements as a supplier, not a Rolex subsidiary. The firm ran independently out of Bienne until Rolex bought it from the Borer family in April 2004. "Aegler" and "Rebberg" refer to the same company — Aegler is the name, Rebberg the street in Bienne where it stood. Aegler also built movements for Gruen, and the architectural sibling of Cal. 300 shipped in the US as the Techni-Quadron under Gruen's own Cal. 877 designation. That shared supplier explains a documented transplant pattern: a Gruen-stamped movement turns up inside a Rolex Prince case now and then. It also explains a real misattribution in the literature — "Cal. 877" occasionally gets listed as a Prince caliber, when it was never a Rolex number at all.
Aegler remained an independent supplier until Rolex bought the company from the Borer family in April 2004. "Aegler" and "Rebberg" refer to the same firm; Rebberg was the street in Bienne where it stood. Aegler also made movements for Gruen. The architectural sibling of Cal. 300 sold in the United States as the Gruen Techni-Quadron, designated Cal. 877. Gruen-stamped movements therefore sometimes appear in Rolex Prince cases, but Cal. 877 was never a Rolex caliber number.


Movement grading across the family runs Prima &rarr; Extra Prima &rarr; Ultra Prima, rising through jewel count, adjustment positions, and chronometer testing rigour. A "Chronometer" or "Observatory" mark on a Prince dial corresponds to Extra Prima or Ultra Prima grade only — a Prima movement never earns it. Rolex submitted Prince movements to the National Physical Laboratory at Kew for rate certificates independent of the Swiss Bureaux Officiels Suisse de Contrôle; the 1914 Class A Kew certificate Rolex commonly cites as its first official chronometer rating belongs to an earlier ladies' wristwatch movement, predating the Prince family, though the Princes continue that Kew-Teddington testing tradition from 1928 forward.
Prince grades run Prima &rarr; Extra Prima &rarr; Ultra Prima, with higher jewel counts, more adjustment positions, and stricter chronometer testing. Only Extra Prima and Ultra Prima watches carry "Chronometer" or "Observatory" dial marks. Rolex submitted Prince movements to the National Physical Laboratory at Kew for rate certificates independent of the Swiss Bureaux Officiels Suisse de Contrôle. Its often-cited 1914 Class A Kew certificate belongs to an earlier ladies' wristwatch movement, while Prince testing at Kew-Teddington began in 1928.


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Cal. 300 is the original Prince movement, 1928 to 1935. Rolex's own factory caliber table lists it under size code "T.S.," the same code shared by Cal. 310 and Cal. 350 below — Christie's calls all three "the same movement base," with parts interchangeable between them and only the balance bridge marking which of the three a given example started as. Grading ran Prima (15 jewels, 6-position) through Extra Prima and Ultra Prima (18 jewels, 6-position, some marked Chronometer); researcher David Boettcher's patent work identifies the three extra jewels precisely — two end-stones on the escape-wheel pivots and one top bearing on the centre wheel. Grade wording moved from the ratchet wheel on early production to the main train bridge later on, itself a rough dating tool. The photographed example, an Extra Prima marked "Observatory 6 Positions," shows the later bridge-stamped convention.
Cal. 300 is the original Prince movement, made from 1928 to 1935. Rolex's factory caliber table places it under the "T.S." size code shared by Cal. 310 and Cal. 350. Christie's describes all three as the same movement base, with interchangeable parts and the balance bridge identifying the original execution. Prima movements have 15 jewels and six-position adjustment; Extra Prima and Ultra Prima versions have 18 jewels, six-position adjustment, and sometimes a Chronometer marking. David Boettcher identifies the additional jewels as two end-stones on the escape-wheel pivots and a top bearing on the centre wheel. Early movements carry the grade wording on the ratchet wheel, while later examples place it on the main train bridge. The photographed Extra Prima, marked "Observatory 6 Positions," shows the later convention.
 
Balance metallurgy changed gradually. Examples from 1928 use a bimetallic balance with a plain Breguet spring; by the mid-to-late 1930s, documented movements have both monometallic and bimetallic balances paired with Elinvar-alloy hairsprings. No exact transition year is established. "Patented Superbalance" on later ratchet wheels and bridges refers to Aegler's Swiss patent CH196706, filed in August 1936 and granted in March 1938. A movement carrying the mark therefore postdates the grant. The recessed timing screws are often said to reduce air resistance, but Boettcher reads the patent as a way to maximize the balance's radius of gyration within the available space.


The balance metallurgy shifted over the run: 1928 examples carry a bimetallic balance with a plain Breguet spring, and by the mid-to-late 1930s Antiquorum lots show both monometallic and bimetallic balances paired with Elinvar-alloy hairsprings — a real transition, but a gradual and overlapping one that the auction record never pins to an exact year. "Patented Superbalance," stamped on later ratchet wheels and bridges, refers to Swiss patent CH196706, filed by Aegler — not Rolex directly — in August 1936 and granted March 1938; a movement so marked postdates that grant. The recessed timing screws are often explained as reducing air resistance, but Boettcher argues the patent's real purpose is maximizing the balance's radius of gyration within a small movement, since a plain-rimmed balance can't grow as large in the same footprint. Cal. 300 carries no shock protection, a systematic absence across roughly fifteen Antiquorum Prince lot descriptions spanning 1989 to 2022 — a catalogue style that names shock-absorbers when they're present — consistent with Incabloc only reaching production in 1938, after the Prince's core design was already set. The winding-stem bridge is Cal. 300's known service fail point: a Prince that sets the time and then immediately disengages points to a broken bridge, not a deeper fault, and aftermarket CNC-machined brass replacement bridges and stems circulate among watchmakers as a routine repair part.
Cal. 300 has no shock protection, consistent with Incabloc reaching production only in 1938, after the core Prince design was established. Its winding-stem bridge is a known service weak point. A movement that sets the time and then disengages may have a broken bridge; watchmakers use aftermarket CNC-machined brass bridges and stems for this repair.


UK auction houses have separately catalogued a cluster of three- and four-digit numbers on 1862, 1490, and 1855 movements — 510, 579, 841, 1004, 1130, and 1439, confirmed against specific Bonhams, Christie's, and Tajan lots below, plus a weaker sighting of 701 and a single-sourced 1759. These are almost certainly movement serial numbers rather than caliber designations, read off the plate by cataloguers and repeated from there; the grouped entry below sets out the evidence. Continental houses (Antiquorum, Christie's Geneva) describe the same class of movement by grade name and the T.S. size code, never by these numbers. Two further numbers sometimes listed alongside them, Cal. 414 and Cal. 527, do not appear in any auction house, dealer, or catalogue record found for the Rolex Prince and are not documented here. A separate case reference, 971A, is sometimes mistaken for a caliber number in secondary listings — the actual movement inside a 971A case is this same T.S./300-family caliber, per Antiquorum's own 1989 cataloguing of one.
Several UK auction catalogues treat the three- and four-digit numbers found on movements in refs 1862, 1490, and 1855 as calibers. The documented numbers are 510, 579, 841, 1004, 1130, and 1439, with weaker evidence for 701 and a single record of 1759. They are almost certainly movement serials read from the plate. Continental catalogues identify the same movement class by grade and the T.S. size code instead. Cal. 414 and Cal. 527 have no documented connection to the Rolex Prince. The number 971A is a case reference, not a caliber; Antiquorum catalogued a 971A in 1989 with the same T.S./300-family movement.


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"T.S." is Rolex's own size-family code for this 16.9 × 32.7mm architecture, printed directly by Christie's as "cal. T.S. Ref. 300" — not, as sometimes assumed, an abbreviation for "Très Soigné"; no source found supports that reading. The Ultra Prima 6-position execution built on this base runs 1932 to 1938: lateral lever escapement, monometallic balance on a micrometer regulator, Breguet overcoil hairspring, rhodium plating. It is documented on the [[Reference:1527|1527 Railway]], where the grade mix inverts the pattern seen on the 1490 — Extra Prima dominates the surviving 1527 population, and an 8-position "Officially Tested in Eight Ways" Ultra Prima example is the outlier at the top of the range, the highest-hammering Prince movement recorded (Mondani 2006, bamboo-bracelet 1931 example, CHF 27,140).
"T.S." is Rolex's size-family code for this 16.9 × 32.7mm architecture, catalogued by Christie's as "cal. T.S. Ref. 300." There is no support for the common expansion "Très Soigné." The six-position Ultra Prima execution ran from 1932 to 1938 with a lateral lever escapement, monometallic balance, micrometer regulator, Breguet overcoil hairspring, and rhodium plating. On the [[Reference:1527|1527 Railway]], Extra Prima movements outnumber Ultra Prima examples, reversing the pattern seen on the 1490. An eight-position Ultra Prima marked "Officially Tested in Eight Ways" is documented on a 1931 bamboo-bracelet example sold by Mondani in 2006.


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The centre-seconds member of the T.S. family, built for the wedge-shaped [[Reference:3361|3361 Aerodynamic]] / 3362 / [[Reference:3937|3937]] Prince group. Antiquorum's own Hong Kong 2000 cataloguing of a 3361 gives it directly: "7 1/2′′′, rhodium plated, 18 jewels, lateral lever escapement, Superbalance balance adjusted to 6 positions, self-compensating Breguet balance-spring, micrometer regulator," 19 × 49mm cased. Antiquorum never prints the number "310" itself in that description — the caliber-number attribution to specific serial examples rests on dealer listings rather than the auction house's own text, worth flagging as weaker than the architecture description around it. Production ended in 1938, but Aegler kept stockpiling movements that Rolex cased into 3361 production through 1952; a 1952-cased example with a movement number far lower than its case number is the stockpile pattern showing up directly in the serial record.
Cal. 310 is the centre-seconds member of the T.S. family, used in the wedge-shaped [[Reference:3361|3361 Aerodynamic]], 3362, and [[Reference:3937|3937]] Prince group. Antiquorum described a 3361 in 2000 as a rhodium-plated 7½-ligne movement with 18 jewels, lateral lever escapement, six-position Superbalance, self-compensating Breguet balance spring, and micrometer regulator, in a 19 × 49mm case. That catalogue does not print the number 310, so the caliber attribution is less secure than the architecture and specifications. Movement production ended in 1938, but Aegler stock remained in Rolex cases through 1952. A 1952 example with a movement number far below its case number illustrates this stockpile pattern.


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Sources disagree sharply on this caliber, and both readings are printed here rather than picking one. Christie's cataloguing of a 1938 ref. 2835 "Prince Elegant" gives a tonneau-shaped 15-jewel movement, and Charles Jarman's ''The Rolex Reference Guide'' (4th edition) describes Cal. 360 at page 94 as "manually wound, small seconds register, tonneau shaped, with a SuperBalance" — the reading behind this page's earlier framing of it as a 1936-onward tonneau-plate successor to Cal. 300, used as a visual dating tell on 971, 1490, 1862, and 3361 cases. Against that, a Rolex factory caliber table lists Cal. 360 as rectangle-shaped, 18 × 27mm — a size class well below the 300 family's 16.9 × 32.7mm — 18 jewels, dated 1937, and marked as its own "Basic Caliber" rather than a 300 derivative. The nickname "HW," popularly explained as Hans Wilsdorf's initials, rests on a single dealer source; the same factory table instead shows a size code that reads as "F-LW" in that document, plausibly an OCR artifact of the same "F" size family that also produces Cal. 180's "F." code — the founder-initials story has no independent support and the size-code reading fits the table's own naming pattern better. The two accounts do converge on one point. Jarman puts the HW's first appearance in 1937 at page 102 of the same book, and the factory table's own date for Cal. 360 is 1937 as well, so the disagreement is over shape and size rather than over when the caliber starts. Dealer-side research argues for an earlier start on the grounds that no all-original HW has surfaced without a SuperBalance, and that the SuperBalance wording drops off the winding wheel from roughly 1938 — a progression said to be visible in the close-up movement photography in Shigeharu Aritake's ''Rolex Scene 1913–1997''. With the architecture itself disputed, escapement and balance detail aren't asserted here either; a firm reading would mean picking a side in a disagreement the sources themselves haven't settled.
The architecture of Cal. 360 is disputed. Christie's describes a 1938 ref. 2835 "Prince Elegant" with a tonneau-shaped 15-jewel movement, and Charles Jarman's ''The Rolex Reference Guide'' (4th edition) calls Cal. 360 a manual, small-seconds, tonneau-shaped movement with a SuperBalance. Rolex's factory caliber table instead lists a rectangular 18-jewel Basic Caliber measuring 18 × 27mm, smaller than the Cal. 300 family's 16.9 × 32.7mm.
 
Both Jarman and the factory table date its introduction to 1937. The disagreement concerns its shape, size, and relationship to Cal. 300. The popular claim that "HW" means Hans Wilsdorf has no independent support; the factory table appears to give the size code as "F-LW," possibly an OCR rendering related to the "F" size-family code used for Cal. 180. Shigeharu Aritake's ''Rolex Scene 1913–1997'' is cited for a progression in which SuperBalance wording disappears from the winding wheel around 1938, but this does not resolve the architecture. Escapement and balance details therefore remain unconfirmed.


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=== Numbered Prince movements (510, 579, 701, 841, 1004, 1130, 1439) ===
=== Numbered Prince movements (510, 579, 701, 841, 1004, 1130, 1439) ===


Seven numbers circulate as Prince "calibers" — 510, 579, 701, 841, 1004, 1130 and 1439. The evidence points to all seven being movement serial numbers that cataloguers have read as caliber designations, and they are grouped here rather than given separate entries for that reason.
Seven numbers circulate as Prince "calibers": 510, 579, 701, 841, 1004, 1130, and 1439. All are most likely movement serial numbers misread as caliber designations, so they are grouped here.


The mechanism is visible on the plates. A survey of thirty-five photographed Prince movements, drawn from UK dealer stock alongside Christie's, Bonhams and aggregated lot records, found no caliber designation on any of them. What a Prince plate carries is a grade legend — Prima, Extra Prima, Ultra Prima, Observatory Quality, Officially Tested in Eight Ways, Timed 6 Positions, For All Climates — together with a jewel count, "Swiss Made", and a bare stamped number in a fixed position beside the "NN RUBIES" legend. That number runs from four digits up to seven. On the Ultra Prima 18-jewel plate family alone it reads 1260, 1439 and 1759 across different examples: three numbers on one movement, two of which this page had been carrying as separate calibers.
Photographed Prince plates carry a grade legend, jewel count, "Swiss Made," and a bare number stamped beside the "NN RUBIES" wording, but no caliber designation. Grade legends include Prima, Extra Prima, Ultra Prima, Observatory Quality, Officially Tested in Eight Ways, Timed 6 Positions, and For All Climates. The bare number ranges from four to seven digits. Ultra Prima 18-jewel examples with otherwise matching plates carry 1260, 1439, and 1759 in that position, confirming that the stamp varies within one movement type.


Three further things line up with that reading. The continental houses never use these numbers, identifying the same class of movement by size code and grade instead — Christie's catalogues it as "cal. T.S. 300" and Antiquorum as "7½′′′ T.S. 300, Observatory Quality". The UK lots that do print a "Cal." figure also print a separate case or serial number in the same description, so the "Cal." figure is a second number read off the movement rather than off the case. And the specifications attached to these numbers collapse into one another: Cal. 1439 and Cal. 1759 are both 18 jewels timed to six positions in the Ultra Prima grade, which is one movement described twice. The same error has been caught in print, in a dealer listing that described a bare mainplate serial stamp as a "1240 calibre movement".
Continental auction catalogues identify these movements by size code and grade, such as "cal. T.S. 300" or "7½′′′ T.S. 300, Observatory Quality." UK lots that print a "Cal." figure also give a separate case or serial number, indicating that the supposed caliber was read from the movement. The specifications also overlap: 1439 and 1759 both describe an 18-jewel Ultra Prima movement adjusted to six positions. A bare mainplate serial has likewise appeared in print as a "1240 calibre movement."


None of this justifies deleting the numbers outright, since a collector meeting "Cal. 1004" in a lot description needs to find it somewhere. The documented sightings are kept below with the catalogue text that produced them, on the understanding that the number in each case is most likely the movement's serial.
The numbers remain useful as search terms because they appear in auction descriptions. Each is listed below as a likely movement serial rather than a distinct caliber.


{| class="wikitable" style="font-size:90%;"
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| stainless steel ref. 1862, circa 1935, case No. 103
| stainless steel ref. 1862, circa 1935, case No. 103
| "17-jewel Cal.579 manual wind movement" (Bonhams London)
| "17-jewel Cal.579 manual wind movement" (Bonhams London)
| single lot; the trailing "T" in some listings is an aggregator-database artifact, absent from Bonhams' own text
| single lot; the trailing "T" in some listings is absent from Bonhams' catalogue text
|-
|-
| 701
| 701
| one dealer photograph showing "ROLEX PRINCE 701" on a 1930s piece
| one photograph showing "ROLEX PRINCE 701" on a 1930s piece
| none
| none
| no jewel count, adjustment count or technical description anywhere; absent from all thirty-five photographed movements, and absent from the auction and catalogue record entirely
| no recorded jewel count, adjustment count, or technical description; no auction or catalogue attribution
|-
|-
| 841
| 841
| ref. 1862 circa 1930, case No. 10403
| ref. 1862 circa 1930, case No. 10403
| "17-jewel Cal.841 manual wind" (Bonhams London; resold through Tajan in 2019, the same watch catalogued twice)
| "17-jewel Cal.841 manual wind" (Bonhams London; resold through Tajan in 2019, the same watch catalogued twice)
| a separate listing gives 15 jewels for a "Cal. 841T" on a different 1862 — the jewel count moves, which a caliber designation would not
| a separate listing gives 15 jewels for a "Cal. 841T" on a different 1862; a caliber designation would not change jewel count
|-
|-
| 1004
| 1004
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Cal. 1759, which keeps its own entry below for the sake of the movement-and-caseback pairing photographed there, is the same phenomenon: it is one of the three numbers found in that serial slot on the Ultra Prima plate, and its lot is single-sourced to one regional UK house.
Cal. 1759 is the same phenomenon. It remains separate because the photographed watch preserves matching movement and caseback markings, but the number appears in the serial position on an Ultra Prima plate and is documented in only one regional UK auction.


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The Ultra Prima Chronometer execution, circa 1937: 18 jewels, 6-position adjustment, documented at Gardiner Houlgate on a 9ct ref. 1862 with Glasgow import hallmarks for 1937, catalogued directly as "cal. 1759 Ultra Prima Chronometer 18 jewel movement timed 6 positions." The photographed example pairs the movement with its original case back, engraved "1759, 18 Rubies, Ultra Prima" alongside "31 Records Universels" and the retailer stamp — a rare survival of movement and original case together. Gardiner Houlgate is a regional UK specialist house rather than one of the major auction rooms, and this number is currently single-sourced to that one lot.
This circa 1937 Ultra Prima Chronometer has 18 jewels and six-position adjustment. Gardiner Houlgate catalogued it in a 9ct ref. 1862 with 1937 Glasgow import hallmarks as a "cal. 1759 Ultra Prima Chronometer 18 jewel movement timed 6 positions." The photographed example retains its matching caseback, engraved "1759, 18 Rubies, Ultra Prima" alongside "31 Records Universels" and a retailer stamp. The identification rests on this single regional UK auction lot.


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The jump-hour member of the T.S. family, alongside Cal. 300 (small seconds) and Cal. 310 (centre seconds) above. Christie's Geneva (14 May 2018, lot 113) and Sotheby's Geneva (November 2016, lot 135) both catalogue it in the [[Reference:1491|1491 Brancard Jumping Hour]] as an 18-jewel, chronometer-rated movement on the T.S. base, in the 1491's rectangular case. A separate 1491 example, movement plate marked "15 Rubies" and Extra Prima rather than Ultra Prima, is catalogued the same way by Christie's (lot 5130736); the jewel count tracks the grade tier rather than a single fixed spec. Watch Wiki notes the jump-hour disc mechanism works on much the same principle the Datejust's date disc would decades later — an early instance of a mechanism Rolex returned to on a completely different watch. Surviving examples carry Glasgow import hallmarks from 1930-31, consistent with the shared T.S. base's own 1928-35 production window.
Cal. 350 is the jump-hour member of the T.S. family, alongside the small-seconds Cal. 300 and centre-seconds Cal. 310. Christie's and Sotheby's catalogue it in the [[Reference:1491|1491 Brancard Jumping Hour]] as an 18-jewel, chronometer-rated movement on the T.S. base. Another 1491 has a "15 Rubies" Extra Prima movement rather than an Ultra Prima, so jewel count follows grade rather than one fixed specification. The jump-hour disc works on much the same principle as the later Datejust date disc. Surviving examples carry Glasgow import hallmarks from 1930–31, consistent with the T.S. base's 1928–35 production window.


Two further notes apply across the whole family rather than to one caliber. The 1491 case runs deeper than the 1490's to house the jump-hour module — that case-depth difference is the canonical way to catch a 1490 retrofitted with a later module and passed off as a genuine 1491. Three module-specific service patterns turn up in the collector record: a weak jump-impulse spring producing a "lazy" disc advance, a worn disc-retention pawl producing hour-disc jitter, and a misaligned dial aperture that reveals fragments of two numerals at once.
The 1491 case is deeper than the 1490 to accommodate the jump-hour module. Case depth therefore distinguishes a genuine 1491 from a 1490 fitted with a later module. Known service faults include a weak jump-impulse spring that causes a "lazy" disc advance, a worn retention pawl that makes the hour disc jitter, and a misaligned dial aperture that exposes parts of two numerals.


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== Bubbleback and early automatic ==
== Bubbleback and early automatic ==


Bubbleback and early Oyster Perpetual references run on a distinct family of early self-winding calibers, separate from the Prince's manual shaped movements and predating the standardized post-war automatic line. The "bubble" in Bubbleback describes the domed caseback these movements needed to clear their automatic rotor — a genuine self-winding mechanism, not a bumper system, at a time when most competing automatics still used one.
Bubbleback and early Oyster Perpetual references use a distinct family of self-winding calibers. They followed the Prince's manual shaped movements and preceded the standardized post-war automatic line. The "bubble" refers to the domed caseback needed to clear the full-rotor automatic mechanism. It was not a bumper system, although many competing automatics still used one.


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The first Bubbleback caliber, debuting in the original 1933 reference 1858 with its three-piece Oyster case: automatic, 19 jewels, 18,000 vph, straight-line lever escapement, Superbalance with a Breguet balance spring, per Antiquorum's own cataloguing of a 3353 example (8¾′′′ rhodium-plated). Documented on the [[Reference:3353|3353]] by case description. Superseded by Cal. 620 as the movement architecture matured through the mid-1930s. No individually-confirmed movement photograph has surfaced for this caliber yet — treat any generic "early Bubbleback movement" image with a 520 label with caution unless the caliber number is visible engraved on the piece.
Cal. 520 debuted in the original 1933 ref. 1858 with its three-piece Oyster case. Antiquorum describes the 8¾-ligne rhodium-plated movement in a [[Reference:3353|3353]] as automatic, with 19 jewels, 18,000 vph, a straight-line lever escapement, and a Superbalance with Breguet balance spring. Cal. 620 superseded it as the architecture developed through the mid-1930s. No confirmed movement photograph is available; a generic early Bubbleback movement should not be identified as a 520 unless the engraved caliber number is visible.


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11½ lignes, 26.4mm diameter, 7.5mm height, 17 jewels (Antiquorum lots range 17-20 across individual examples), 18,000 vph, 35 hours of reserve, derived from the manual-wind Cal. 600. Straight-line lever escapement, monometallic Superbalance, Breguet balance spring — the regulator changes across the run, a swan-neck micrometer regulator and no shock protection on earlier 1940s examples, an index regulator with a shock absorber added by the early 1950s. The rotor is the defining feature: a uni-directional "Perpetual" weight that spins a full 360 degrees with no bumpers or buffers, at a time when competing automatics still relied on bumper systems. It's engraved "ROLEX PERPETUAL / CHRONOMETER / SWISS MADE / PATENTED / SUPER-BALANCE," and an 18mm cover plate held by three screws carries its own "VIS TIRETTE / PATENTED / TRIGGER SCREW" marking. Cal. 620 powered the original 1931 "Perpetual" and the early Bubbleback generation, and is the base architecture Cal. 630 (and the related 635, 645) evolved from directly.
Derived from the manual Cal. 600, Cal. 620 became the base for Rolex's early full-rotor automatic family. Antiquorum catalogues individual examples with 17 to 20 jewels, against the table's 17-jewel specification. Earlier 1940s movements have a swan-neck micrometer regulator without shock protection; by the early 1950s, an index regulator and shock absorber appear.
 
Its defining feature is a unidirectional "Perpetual" rotor that turns through 360 degrees without bumpers or buffers. The rotor is engraved "ROLEX PERPETUAL / CHRONOMETER / SWISS MADE / PATENTED / SUPER-BALANCE," while the three-screw, 18mm cover plate reads "VIS TIRETTE / PATENTED / TRIGGER SCREW." Cal. 620 powered the original 1931 "Perpetual" and early Bubblebacks. Cal. 630 and the related 635 and 645 developed from the same architecture.


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Launched 1937, 26.0mm, 17 jewels (Grail Watch Wiki gives 17; WatchGuys lists 18 for the same caliber, a documented count discrepancy between sources), COSC-certified, adjusted to 7 positions, Breguet hairspring. Evolved directly from the Cal. 620 base (Caliber Corner groups 620, 630, 635, and 645 as one related family), and shares its predecessor's cover-plate marking: "Vis Tirette *** Patented *** Trigger Screw." The rotor and bridge carry the same "Rolex Perpetual Chronometer, Swiss Made, Patented, Super-Balance" signature as the 620, which makes the two easy to mix up without checking the caliber number stamped in the small box on the bridge itself.
Launched in 1937, Cal. 630 was chronometer-certified under the period Swiss testing system, adjusted to seven positions, and fitted with a Breguet hairspring. One secondary source gives 18 jewels rather than the table's 17. The movement developed directly from Cal. 620 and shares its "Vis Tirette *** Patented *** Trigger Screw" cover-plate marking. Its rotor and bridge also carry the same "Rolex Perpetual Chronometer, Swiss Made, Patented, Super-Balance" signature. The caliber number stamped in the small box on the bridge distinguishes the two.


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An Aegler-supplied 10½-ligne hand-wound family, 700 / 710 base architecture: straight-line lever escapement, monometallic Superbalance adjusted to 6 positions, self-compensating Breguet balance spring, swan-neck micrometer regulator — the chronometer-grade fitting, per Antiquorum's own cataloguing of both a bare Cal. 700 movement and a cased 10½-ligne hunter example — and no shock protection named. It powers the originating Air-King 4925 and its Air-Lion / Air-Tiger / Air-Giant siblings — the 4365 sub-seconds, 4444 mid-size, and 4647 Hunter Precision — sitting architecturally between the pre-war Prince and Bubbleback shaped calibers and the post-war 1030 automatic. Rolex's own factory caliber table dates 700 and 710 to 1938 rather than the wider 1945-53 window sometimes quoted, and lists Cal. 720 separately as an automatic with shock protection — a different caliber from this manual pair, not a third member of it, contra how this family is sometimes grouped.
This Aegler-supplied 10½-ligne hand-wound family uses the 700/710 architecture. It has a straight-line lever escapement, monometallic Superbalance adjusted to six positions, self-compensating Breguet balance spring, and swan-neck micrometer regulator, with no documented shock protection. The movement powers the original Air-King 4925 and its Air-Lion, Air-Tiger, and Air-Giant siblings, including the sub-seconds 4365, mid-size 4444, and 4647 Hunter Precision. Architecturally, it sits between the pre-war Prince and Bubbleback movements and the post-war automatic Cal. 1030. Rolex's factory caliber table dates Cal. 700 and 710 to 1938. It lists Cal. 720 separately as an automatic movement with shock protection, not as a third member of this manual pair.


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A 9&frac34;-ligne manual caliber, one size class below the 10&frac12;-ligne 700/710/720 family above, fitted with a patented Super Balance. Sotheby's November 2025 sale of the Mercedes Gleitze Oyster ($1.73 million, via Robb Report) catalogues the movement as a Hunter-architecture base upgraded to Cal. 600, rhodium-finished, in a 27mm case made in late 1926 &mdash; the watch Gleitze wore on her 21 October 1927 Channel swim attempt, caseback engraved "Miss M. Gleitze / The Companion 'Oyster.' Vindication Channel Swim. October 21st. 1927."
Cal. 600 sits one size class below the 10&frac12;-ligne 700/710/720 family and carries a patented Super Balance. Sotheby's catalogued the movement in the Mercedes Gleitze Oyster in November 2025 as a rhodium-finished Hunter-architecture base upgraded to Cal. 600. The late-1926 27mm case belongs to the watch Gleitze wore during her 21 October 1927 Channel swim attempt and is engraved "Miss M. Gleitze / The Companion 'Oyster.' Vindication Channel Swim. October 21st. 1927."


Rolex's factory caliber table lists Cal. 600 as a Basic Caliber rather than a derivative &mdash; manual wind, small seconds, 21.7mm, 17 jewels, entered 1933, under a Hunter-patent size bracket. Basic Caliber is the load-bearing word: 600 is the root the whole 9&frac34;-ligne automatic branch grows from, with Cal. 620 (1936) taken directly off it and 635, 640 and 645 (all 1950) descending through that line. The 17-jewel count is one of the few figures in this part of the catalogue that two independent sources agree on outright, the factory table and Sotheby's Gleitze lot giving the same number.
Rolex's factory table lists Cal. 600 as a Basic Caliber: manual wind, small seconds, 21.7mm, 17 jewels, entered in 1933 under a Hunter-patent size bracket. It is the root of the 9&frac34;-ligne automatic branch. Cal. 620 followed in 1936, with Cal. 635, 640, and 645 descending from that line in 1950. Both the factory table and Sotheby's Gleitze catalogue give 17 jewels.


The 1933 date is what makes the Gleitze watch interesting rather than simply old. The case carries Glasgow import marks for 1926/1927 and the swim was October 1927, but the caliber inside is one the factory table does not start until 1933, and the Super Balance stamped on it belongs to Aegler's Swiss patent CH196706, not filed until August 1936 and not granted until March 1938. The movement in that watch is therefore a later service replacement by a decade or more, which squares with the mid-1970s Rolex service box that accompanied the lot. The provenance is the case and the engraving; the movement is a survivor of Rolex's own aftercare.
The Gleitze case carries Glasgow import marks for 1926/1927, but its movement is later. Rolex's factory table dates Cal. 600 to 1933, and the stamped Super Balance refers to Aegler's Swiss patent CH196706, filed in August 1936 and granted in March 1938. The movement is therefore a service replacement fitted at least a decade after the 1927 swim. A mid-1970s Rolex service box accompanied the watch. Its historical provenance rests on the case and engraving, not on the present movement.


Two of the four mechanical fields stay open here, and the sources do not close them. No 600-specific lot description names the escapement or the regulator, and the factory table has no column for either. Its immediate derivative Cal. 620 is documented as a straight-line lever with a micrometer regulator on earlier examples giving way to an index later, which is the closest the record comes without guessing. Shock protection is a firmer negative: the factory table flags shock-protecting construction on the 1950 calibers in this branch and does not flag it on the 600, consistent with a design fixed years before Incabloc reached production in 1938.
The escapement and regulator remain undocumented. Cal. 620, its immediate derivative, uses a straight-line lever and changes from a micrometer regulator to an index regulator, but those details cannot be assigned to Cal. 600 without direct evidence. Shock protection is more likely absent: the factory table flags it on the 1950 calibers in this branch but not on Cal. 600, whose design predates Incabloc production in 1938.


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1953–55, 19 jewels, 18,000 vph, 36 hours of reserve, 26.4mm — the caliber in the first Submariner references, 6204 and 6205. Straight-line lever escapement, monometallic Superbalance, blued-steel self-compensating Breguet overcoil, index regulator, shock absorber — confirmed across Antiquorum and Sotheby's lot descriptions of both references. "A.260" is itself Rolex's size-family code for this movement class rather than a caliber number in the ordinary sense, which is why auction houses write "cal. A260" the same way they write "cal. T.S." for the Prince family. Its rotor is "non-butterfly," visually distinct from the butterfly-rotor Cal. 1030 that follows it. Hodinkee describes A260 as repurposed from earlier Oyster Perpetual models including later Bubblebacks, rather than a clean-sheet design for the Submariner.
A260 powered the first Submariner references, 6204 and 6205, from 1953 to 1955. "A.260" is Rolex's size-family code for this movement class rather than a conventional caliber number, much like "T.S." in the Prince family. Its non-butterfly rotor distinguishes it from the butterfly-rotor Cal. 1030. Hodinkee describes A260 as an adaptation of a movement used in earlier Oyster Perpetuals and later Bubblebacks, rather than a design made specifically for the Submariner.


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1952&ndash;55, 18 jewels, 18,000 vph, 36 hours, 29.5mm, a full-rotor uni-directional Perpetual, not a bumper caliber despite sometimes being described as one &mdash; a confusion with Bubbleback-era geometry. A296 powers the Big Crown 6200 and the earliest Explorers (6098, 6150 "Precision," 6298, 6350), and the earliest Datejusts, 6104 and 6105, with the 6150 and 6350 showing the identical movement in non-COSC and COSC form. Some auction and dealer listings write "Cal. 775" instead of "Cal. A296" for the same movement on the same watches &mdash; A.296 is Rolex's size-family code and 775 the commercial number, not two different calibers. Cal. 1030 succeeds it from 1955 with bidirectional winding via a butterfly rotor and a thinner autowind module; that thickness reduction is specifically what eliminates the domed Bubbleback caseback profile going forward &mdash; Phillips' Geneva Watch Auction FOUR framed the A296-to-1030 swap explicitly as a thickness change, not a different winding concept.
Made from 1952 to 1955, A296 powered the Big Crown 6200, early Explorers 6098, 6150 "Precision," 6298, and 6350, and early Datejusts 6104 and 6105. Its full rotor winds in one direction; it is not a bumper caliber. The 6150 and 6350 use the same movement in non-COSC and COSC forms. "A.296" is Rolex's size-family code and 775 its commercial number, so listings may use either designation for the same movement. Cal. 1030 replaced it in 1955 with bidirectional winding, a butterfly rotor, and a thinner automatic module. Phillips identifies that reduced thickness as the change that eliminated the domed Bubbleback caseback.


The mechanical description repeats almost verbatim wherever a house catalogues the movement under its size code: straight-line lever escapement, monometallic balance, self-compensating Breguet balance spring, index regulator. Bonhams gave exactly that for a 6105 in London in May 2013, Sotheby's for another 6105 in Geneva in May 2010, and Antiquorum for a 6104. Lots catalogued under the commercial number 775 add two things the A.296-labelled ones leave out &mdash; a balance adjusted to 6 positions and a shock absorber &mdash; and they add them consistently: Antiquorum in New York in December 2009, Sotheby's in New York in June 2006 and Artcurial in Monaco in July 2013 all list both for 6350 Explorers, and Rolex's own factory caliber table flags REF. 775 as shock-protecting. The split tracks which designation the cataloguer reached for rather than two builds of the movement. That same factory table settles the size-code question from the other direction by putting A.296 on Cal. 765 as well, the calendar-equipped version at the same 29.5mm and 18 jewels &mdash; a size code covering two commercial numbers, which is what a size code is supposed to do.
The movement has a straight-line lever escapement, monometallic balance, self-compensating Breguet balance spring, and index regulator. Catalogues using the commercial number 775 also specify six-position adjustment and a shock absorber, and Rolex's factory table marks ref. 775 as shock-protected. This reflects different naming conventions rather than separate builds. The same factory table assigns the A.296 size code to Cal. 765, a calendar movement with the same 29.5mm diameter and 18-jewel count, confirming that the code covers more than one commercial caliber.


Balance metallurgy is where the caliber connects back to the Prince era. Christie's, describing a 6150 in Hong Kong in November 2007, calls the balance a "patented Super-balance," the same Aegler patent CH196706 that governs [[#cal-300|Cal. 300]]'s recessed timing screws, filed in August 1936 and granted in March 1938. Jewel counts printed for the movement scatter badly and should not be read as variants: 18 and 19 turn up for the going train, 2 and 7 for the rotor module, and one Christie's description of a 6150 spells the arithmetic out as a 19-jewel movement with a 2-jewel auto module. The factory table's figure, 18, counts the base plate alone.
Christie's describes a 6150 balance as a "patented Super-balance," linking it to Aegler patent CH196706 and the recessed timing screws used on [[#cal-300|Cal. 300]]. Published jewel counts vary because some catalogues separate the going train from the automatic module. Figures of 18 and 19 appear for the base movement, with another two or seven assigned to the rotor module. One 6150 is described as a 19-jewel movement with a two-jewel automatic module. The factory table's figure of 18 counts the base plate alone.


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A sibling of Cal. 630 sharing the same base Cal. 600 architecture and A.260 size code as Cal. 635 above it, distinguished by function rather than grading tier: 630 is sweep-seconds without shock protection, 635 is small-seconds with shock protection, 645 is sweep-seconds with shock protection. Powers the semi-Bubbleback Oyster Perpetual 6084, 6085, and 6284, roughly 1948-1953. Jewel counts vary 17-20 across auction listings for the same caliber, consistent with market-specific tariff variants documented elsewhere in this family.
Cal. 645 belongs to the Cal. 600 family and shares the A.260 size code with Cal. 635. The distinctions are functional: Cal. 630 has sweep seconds without shock protection, Cal. 635 has small seconds with shock protection, and Cal. 645 combines sweep seconds with shock protection. Cal. 645 powered the semi-Bubbleback Oyster Perpetual refs 6084, 6085, and 6284 around 1948–1953. Auction catalogues give 17 to 20 jewels, consistent with both differing counting conventions and market-specific tariff variants found elsewhere in the family.


Four houses describe the movement in near-identical terms, which for a caliber this obscure is unusually good coverage: straight-line lever escapement, Superbalance timed to 6 positions, shock absorber, self-compensating Breguet balance spring, index regulator. Bonhams gave that reading twice, in Knightsbridge in December 2005 for a 6284 and in New York in June 2008 for a 6085; Sotheby's matched it in New York in June 2007, again for a 6085; and Gros &amp; Delettrez in Paris in November 2009 catalogued a 6284 the same way, swapping "monometallic balance timed to 6 positions" for the Superbalance wording. The two phrasings describe the same part &mdash; Superbalance is a monometallic balance with recessed timing screws, not a separate metallurgy.
The movement uses a straight-line lever escapement, Superbalance adjusted to six positions, shock absorber, self-compensating Breguet balance spring, and index regulator. Some catalogues use "monometallic balance timed to 6 positions" instead of Superbalance. Both describe the same part: Superbalance is a monometallic balance with recessed timing screws, not a separate metallurgy.


Rolex's factory caliber table sharpens the lineage a step beyond the sibling framing above. It gives Cal. 635 as 645's immediate base and Cal. 600 as the root that 635 itself descends from, so the family reads 600 to 635 to 645 rather than 645 branching straight off the root. The table also puts the A.260 size code on 635, 640 and 645 together at 26.4mm and 18 jewels, all three entered in 1950, and flags every one of them shock-protecting &mdash; the feature that separates the 1950 A.260 group from the 1936-vintage Cal. 620 base is the shock system, and the table records it that way explicitly.
Rolex's factory table gives the lineage as Cal. 600 to 635 to 645. It places Cal. 635, 640, and 645 under the A.260 size code at 26.4mm and 18 jewels, all entered in 1950 and all shock-protected. The shock system separates this 1950 A.260 group from the 1936 Cal. 620 base.


The jewel spread has a second explanation running alongside the tariff-variant one. Catalogues in this family sometimes quote the base-plate count and sometimes the total including the winding module, and occasionally itemise both: Bonhams describes the closely-related [[#cal-745|Cal. 745]] as "18 jewels plus 7 rotor jewels" in so many words. A Bonhams listing giving a 6085 "Calibre 645, 20 jewels, superbalance" against the factory table's 18 is the same arithmetic seen from either end, not necessarily a different movement.
Jewel counts also vary according to whether a catalogue includes the automatic module. Bonhams describes the related [[#cal-745|Cal. 745]] as "18 jewels plus 7 rotor jewels." Its 20-jewel description of a Cal. 645 in a 6085, against the factory table's 18, does not necessarily indicate a different movement.


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The caliber behind the original Datejust: introduced 1945 with reference 4467, carrying Rolex's first automatic date mechanism in a wristwatch. Base architecture 720/730, size code A.295 &mdash; the slightly earlier sibling of the A.296 group above.
Cal. 740 powered the original Datejust ref. 4467, introduced in 1945 with Rolex's first automatic wristwatch date mechanism. It uses the 720/730 base architecture and the A.295 size code, the earlier sibling of the A.296 group.
 
The 10&frac12;-ligne rhodium-plated movement has a straight-line lever escapement, Superbalance adjusted to six positions, and self-compensating Breguet balance spring. Some catalogues substitute "monometallic balance adjusted to 6 positions" for Superbalance, as they do for Cal. 645. No Cal. 740 description names the regulator; the related A.295-coded movement in ref. 6075 uses an index regulator.


Antiquorum has catalogued the movement in the 4467 twice in near-identical language, in Geneva in November 2002 and in Hong Kong in June 2002: rhodium-plated, straight line lever escapement, Superbalance adjusted to 6 positions, self-compensating Breguet balance-spring, at 10&frac12; lignes. A third description of the same caliber substitutes "monometallic balance adjusted to 6 positions" for the Superbalance wording, the same interchangeable pair seen on Cal. 645. No 740 lot description names a regulator, but the A.295-coded movement in reference 6075 is catalogued with an index regulator, which is the nearest documented neighbour.
The jewel count differs by convention. Antiquorum gives 26, while Rolex's factory table gives 18; the higher figure likely includes the winding module, as Bonhams itemises the related [[#cal-745|Cal. 745]] as "18 jewels plus 7 rotor jewels."


Two numbers in the record refuse to reconcile, and both are worth carrying rather than choosing between. The first is the jewel count: those Antiquorum lots give 26, Rolex's factory caliber table gives 18. The counting convention explains it &mdash; Bonhams itemises the sister [[#cal-745|Cal. 745]] as "18 jewels plus 7 rotor jewels," so a catalogue quoting the mid-twenties is counting the winding module and the factory figure is not. The second is harder. The factory table enters Cal. 740 in 1950 and its 720 and 730 base calibers in 1945, which puts the caliber five years behind the 4467's own 1945 launch. Either the earliest 4467s left with a 720-series movement and the 740 arrived partway through the reference's run, or the table's date is wrong. Nothing in the published record decides between them, and lot descriptions for surviving 4467s name the 740 without addressing when it went in.
The production date remains unresolved. Rolex's factory table enters Cal. 740 in 1950 and its Cal. 720 and 730 bases in 1945, five years after the ref. 4467 launch. Early 4467s may have used a 720-series movement before Cal. 740 arrived, or the table date may be wrong. Published descriptions of surviving 4467s do not settle the sequence.


One absence carries its own weight. The factory table flags both 720 and 730 as shock-protecting and does not flag the 740, and the 4467 lot descriptions likewise stop at the balance spring without mentioning a shock absorber &mdash; in a catalogue style that names shock systems when they are there. That points to an unprotected balance, though a negative drawn from two silences is weaker than a positive drawn from a movement in hand, and it should stay unconfirmed until one is examined.
Shock protection is unconfirmed. The factory table flags it for Cal. 720 and 730 but not Cal. 740, and ref. 4467 catalogue descriptions do not mention a shock absorber. These omissions suggest an unprotected balance but do not prove it.


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A calendar-equipped update to Cal. 740, sharing a balance-staff and stem parts group with the whole 700/710/720/730/740/760/765/775 family. Rolex's factory caliber table gives it the A.295 size code, 29.5mm, 18 jewels, entered 1950, built off a 720-740 base and specified as self-winding with sweep seconds and a calendar &mdash; the date complication is the whole point of the number, since the 740 beneath it is a chronometer sweep-seconds movement with no calendar work.
Cal. 745 adds a calendar to Cal. 740 and shares balance-staff and stem parts with the 700/710/720/730/740/760/765/775 family. Rolex's factory table assigns it the A.295 size code and a 1950 entry date. It is based on the 720–740 architecture; Cal. 740 has no calendar.


The single most useful description comes from Bonhams in February 2014, cataloguing a reference 6305: rhodium-plated, 18 jewels plus 7 rotor jewels, straight-line lever escapement, Superbalance, shock absorber, self-compensating blued steel Breguet balance-spring, index regulator. That one line covers all four mechanical fields, and the itemised jewel count is the key that unlocks the rest of this family's arithmetic &mdash; it is the only description in the group that separates the base plate from the winding module instead of publishing one merged figure, which is why counts of 18, 25 and 26 all circulate for movements of the same build. Blued steel for the balance spring rather than the white metal seen later is a period marker in its own right.
Bonhams describes a Cal. 745 in a ref. 6305 as rhodium-plated, with 18 jewels plus seven rotor jewels, a straight-line lever escapement, Superbalance, shock absorber, self-compensating blued-steel Breguet balance spring, and index regulator. Separating the base movement from the winding module explains why totals of 18, 25, and 26 appear for the same build. The blued-steel balance spring is also a period marker, preceding the white-metal springs seen later.


The references it appears on in the auction record are the Datejust "Ovettone" group. A 6305 in 18K yellow gold, case 97602, circa 1955, is catalogued with an 18-jewel Cal. 745; a 6105 carrying Glasgow import marks for 1952 gives the same 18-jewel Cal. 745, movement H78230; and a 6304 from circa 1955, movement 99698/H46452, gives it again. Reference 6105 is the interesting one, because other lots for that same reference are catalogued under Cal. A296 instead &mdash; the 6105 sits on the boundary between the A.295 and A.296 size groups and the auction record splits accordingly. An attribution of Cal. 745 to reference 6039 also circulates, but no lot description supports it and 6039 does not surface as a Rolex reference anywhere in the auction record. It should be read as unverified.
Cal. 745 appears in the Datejust "Ovettone" group. Documented examples include a circa 1955 18K yellow-gold ref. 6305, case 97602; a ref. 6105 with 1952 Glasgow import marks and movement H78230; and a circa 1955 ref. 6304 with movement 99698/H46452. Other ref. 6105 examples use A296, placing the reference across the boundary between the A.295 and A.296 groups. The claimed Cal. 745 fitment in ref. 6039 is unverified; no supporting lot description or confirmed Rolex ref. 6039 has been identified.


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== Oyster and Oysterdate Precision ==
== Oyster and Oysterdate Precision ==


Precision is Rolex's non-chronometer manual line, a 10½-ligne family built alongside the automatic Bubbleback generation rather than after it, and the line that closed out hand winding inside the Oyster case — the Oysterdate Precision 6694 ran to the end of the 1980s, a year past the hand-wound Daytona, and an auction lot survives with its original box and a 1990/1991 Rolex calendar card. The wider claim attached to the 6694, that it is the last manual-wind Rolex of any kind, does not survive checking. It traces to dealer copy rather than to any Rolex document, and Rolex kept selling manual-wind watches for two more decades: the Cellini Danaos on Cal. 1602 into 2008, and the Cellini Prince on Cal. 7040, introduced in 2005 and discontinued a decade later, which unlike anything in this family was a certified chronometer. This family's own architecture outlived the Oysterdate too, in the small-seconds Cal. 1240 that ran the platinum Cellini Cellinium 5240 and 5241. Seven commercial numbers cover the group, distinguished by seconds placement, date, and beat rate rather than by separate architectures, and Rolex's surviving factory parts plates head every one of them — 1200, 1215, 1220, 1225 and 1240 — with the words "Base Calibre 1210."
Precision is Rolex's non-chronometer manual line, a 10½-ligne family built alongside the automatic Bubblebacks. The Oysterdate Precision 6694 remained in production through the end of the 1980s, a year beyond the hand-wound Daytona; one surviving lot includes a 1990/1991 Rolex calendar card. It was not the last manual-wind Rolex. The Cellini Danaos used Cal. 1602 into 2008, while the chronometer-certified Cellini Prince used Cal. 7040 from 2005 until about 2015. The small-seconds Cal. 1240 also carried this architecture into the platinum Cellinium 5240 and 5241. Seconds placement, date and beat rate distinguish the seven commercial numbers. Rolex's parts plates identify Cal. 1210 as the base for 1200, 1215, 1220, 1225 and 1240.


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Rolex's own parts plates settle the family tree. The sheet for every other member — 1200, 1215, 1220, 1225 and the later 1240 — is headed "Base Calibre 1210," and the 1210's sheet is headed with its own number. Fratello and Horbiter disagree in print over whether Cal. 1200 or Cal. 1210 is the architectural base of the group; the factory documentation reads for the 1210, with the small-seconds 1200 filed as a derivative rather than an ancestor.
Rolex's parts plates identify Cal. 1210 as the family's architectural base and file the small-seconds 1200 as a derivative. This resolves a published disagreement between Fratello, which names 1200 as the base, and Horbiter, which names 1210.


The plate gives Ø23.80mm and 4.27mm high, 18,000 vph, centre seconds, 18 jewels. That last figure is the family's standing oddity: Rolex specifies 18 jewels for the two no-date calibers and 17 for the two date calibers, while the movements themselves are signed "Seventeen Jewels" and every catalogued lot found across Antiquorum, Christie's, Sotheby's, Bonhams and Phillips reads 17 without a single exception. Both executions are documented; nothing found reconciles which watches got which, though the same period saw Rolex stamp some movements "UNADJUSTED" purely to sit under a lower American import duty, and jewel count was taxed on the same schedule.
The jewel count remains unclear. Rolex specifies 18 jewels for the two no-date calibers and 17 for the date versions, yet known movements are signed "Seventeen Jewels" and major-house catalogues consistently give 17. Both counts are documented, but their distribution among watches has not been established. Contemporary American import duties taxed jewel count and also account for the "UNADJUSTED" stamps found on some movements.


Antiquorum's cataloguing formula for the caliber runs "straight-line lever escapement, monometallic balance, shock absorber, self-compensating Breguet balance spring," repeated word for word across lots dated from 1946 into the 1970s. Rolex's bilingual plate for the sibling Cal. 1200 names the material outright — a Glucydur balance, supplied either bare and pivoted or complete with Breguet hairspring and regulated. Regulation is conventional index-and-stud with adjusting washers in five thicknesses, not free-sprung; Rolex's own ''Technical and Service Information'' reserves the Microstella system for its 12½-ligne chronometers, which this caliber is not.
The balance is Glucydur with a Breguet overcoil, as specified on the sibling Cal. 1200 plate. Regulation uses a conventional index and movable stud, with adjusting washers in five thicknesses. It is not free-sprung; Rolex reserved Microstella for its 12½-ligne chronometers.


The plate turns up two details the secondary literature misses. The escapement is more thoroughly jewelled than the price class suggests — the pallet fork runs in jewels, and the escape wheel sits in shock-mounted settings with cap jewels on both pivots, the same treatment given the balance. And the centre seconds is indirect, driven off the fourth wheel through a friction-sprung pinion, which is why a perfectly healthy example can show a fluttering seconds hand. The earliest movements carry no shock protection at all: Antiquorum's 1946 ref. 4560 lot, which also supplies the family's only catalogued ligne size at 10½′′′, describes the movement without one.
The pallet fork runs in jewels, while the escape wheel has shock-mounted settings and cap jewels on both pivots, matching the treatment of the balance. Indirect centre seconds, driven from the fourth wheel through a friction-sprung pinion, can produce seconds-hand flutter even in a healthy movement. The earliest examples may lack shock protection; Antiquorum's 1946 ref. 4560 description names none.


Auction lots place the caliber in refs 3745, 4560, 6420, 6422, 6426/6427, 6466, 6480, 6482, 6494, 9083 and 9659, and — against the shorthand pairing the 6694 only with later calibers — Bonhams catalogues a 6694 with a III.60 caseback date on Cal. 1210. An early Crott-catalogued ref. 6082 is also given to this caliber, though Antiquorum and EveryWatch both catalogue 6082 examples on Cal. 710 instead.
Documented fitments include refs. 3745, 4560, 6420, 6422, 6426/6427, 6466, 6480, 6482, 6494, 9083 and 9659. Bonhams also records a ref. 6694 with a III.60 caseback date on Cal. 1210. Ref. 6082 is disputed: Crott assigns one example to 1210, while Antiquorum and EveryWatch catalogue the reference with Cal. 710.


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Cal. 1210 with a calendar added, the extra mechanism accounting for the jump from 4.27mm to 5.07mm in height. Rolex's plate for it makes the relationship literal: the sheet runs to two pages and lists nothing but the calendar parts — an enlargement ring, a date indicator seating, date discs, a set of screws and a date jumper screw — with everything else deferred to the 1210 plates. The date discs alone come in three finishes, champagne, silvered, and champagne printed in red and black, which is the sort of variation that survives on watches long after the paperwork is lost.
Cal. 1215 adds a calendar to the 1210, increasing movement height from 4.27mm to 5.07mm. Its two-page parts sheet covers only the calendar mechanism and defers the rest to Cal. 1210. Date discs came in champagne, silvered, and champagne with red-and-black printing.


The hairspring is the one point where the sources fight. By plate inheritance the 1215 takes the 1210's Breguet overcoil, since its own sheet specifies no balance; Antiquorum has catalogued a 1215 both ways, describing the movement in a ref. 9996 lot as having a "self-compensating flat balance spring, index regulator" and elsewhere giving the Breguet wording it uses for the 1210. That ref. 9996 entry is the only lot in the family to name a regulator type at all, and no lot anywhere describes any of these calibers as free-sprung.
The hairspring is disputed. The parts plates imply the 1210's Breguet overcoil because the 1215 sheet specifies no separate balance. Antiquorum describes one ref. 9996 with a flat hairspring and index regulator, but uses Breguet wording elsewhere. No catalogue describes the caliber as free-sprung.


The date is non-quickset and does not snap. The calendar wheel carries a pawl pin that comes round once in 24 hours and engages a tooth on a star wheel under the date disc, dragging it into place over roughly forty minutes before a jumper spring seats it — the same arrangement Rolex used through the 7xx, 1035 and 11xx calibers, with the instantaneous change arriving only with the 1065/1066 and the 15xx family. An owner reporting that the date starts creeping at 11.20 is describing correct behaviour, not a fault.
The non-quickset date changes progressively rather than snapping at midnight. A pawl on the calendar wheel engages a star wheel beneath the date disc, moving it over roughly forty minutes before the jumper spring seats it. Rolex used the same arrangement in the 7xx, 1035 and 11xx families; instantaneous change arrived with the 1065/1066 and 15xx calibers. A date that begins moving around 11:20 is therefore operating normally.


Christie's brackets the changeover inside ref. 6494 tightly, cataloguing a circa-1956 example on Cal. 1210 and a circa-1958 example on Cal. 1215. Beyond the 6494 the caliber appears in the Speedking 6430, early 6694 production, and the 9996/9919. The claim that it also powered the first Oysterdates, refs. 6094 and 6294, is contradicted by the auction record: Antiquorum catalogues 6094 examples on Cal. 740 and a 6294 on Cal. 790, and 6294 lots carry an "adjusted to two positions, overcoil hairspring" formula this family never uses.
Christie's places the ref. 6494 changeover between a circa-1956 example with Cal. 1210 and a circa-1958 example with 1215. Other documented fitments include the Speedking 6430, early 6694 production, and refs. 9996/9919. Refs. 6094 and 6294 used Cal. 740 and 790 respectively, rather than 1215.


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Cal. 1216 is the family's genuine blank. It is often described as a 17-jewel variant of Cal. 1215, architecturally identical — a claim with no traceable source behind it, and one this page can no longer support.
Almost nothing is known about Cal. 1216. The common description of it as a 17-jewel Cal. 1215 variant has no traceable support.


What can be checked runs both ways. Against the caliber: Rolex's surviving parts-plate library covers 1200, 1210, 1215, 1220, 1225 and 1240 and skips 1216 entirely, and no lot at Antiquorum, Christie's, Sotheby's, Bonhams or Phillips describes a Rolex Cal. 1216. The one auction hit that looks right, a Heritage listing headed "Rolex Ref. 1216," is a case reference rather than a caliber. There is also a live collision to be careful of: Ronda's contemporaneous mechanical series ran 1211, 1213, 1215, 1216, 1217, 1218 and onward, so a Ronda 1216 sitting next to a Ronda 1215 is exactly the shape that manufactures a phantom Rolex sibling.
Rolex's surviving parts plates cover 1200, 1210, 1215, 1220, 1225 and 1240, but omit 1216. No major-house lot identifies a Rolex Cal. 1216, and Heritage's apparent example is a case reference. Confusion is also possible with Ronda's contemporary 1216 movement.


For the caliber: the watch-material trade carries it as a Rolex number. Cas-Ker's genuine-parts catalogue indexes Rolex 1216 between 1215 and 1220 in a list whose every other entry is a real Rolex caliber, and stocks a crown wheel screw under part number 1216.5420 — caliber-prefixed in Rolex's own numbering convention, which is not the kind of thing a supplier invents.
The parts trade nevertheless records it as a Rolex number. Cas-Ker's genuine-parts catalogue places 1216 between 1215 and 1220 and lists crown-wheel screw 1216.5420, following Rolex's caliber-prefixed numbering convention.


The honest reading is that Rolex designated a Cal. 1216 and that almost nothing about it has survived into the public record. Jewel count, seconds layout, beat rate and the references it went into are all unknown here, and anything stated about them elsewhere should be treated as inherited from the 1215 rather than observed.
Rolex therefore appears to have designated a Cal. 1216, but its jewel count, seconds layout, beat rate and fitments remain unknown. Published specifications derived from the 1215 are unconfirmed.


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The Cal. 1210 platform run at a raised beat rate and rebuilt around a different oscillator. The beat-rate question that hung over this caliber is now closed from two directions in Rolex's own paperwork: the factory parts plate is headed "Train: 21.600," and the third edition of Rolex's ''Technical and Service Information'' (1978) lists "Caliber 1220 — 10½″ round — Manual-winding, 21,600 beat" in its table of current calibers. The stray 19,800 vph figure traces to a single machine-translated trade blog and is almost certainly contamination from the 1520, 1570 and 1600, which genuinely run at that rate.
Cal. 1220 raises the 1210 platform to 21,600 vph and uses a different oscillator. Both its parts plate and the 1978 third edition of Rolex's ''Technical and Service Information'' give that rate. The sometimes-published 19,800 vph figure is unsupported.


The oscillator is where the 21,600 generation parts company with the 18,000 one. Where the 1210 carries a screwed Glucydur balance with a Breguet overcoil, this generation runs a screwless smooth-rimmed balance with a flat hairspring, fine-timed by two inertia blocks set into the balance arms — supplied as a gilt and a nickel-plated pair, so the watchmaker can tell which is which at the bench. Rolex describes the same two-block arrangement on its 1520 and 1600, turned with a fine blade and good for roughly ten seconds a day across the full range of adjustment, with the index regulator handling anything larger. Horbiter reaches the same conclusion from the other end, describing the 1220 as the 1210 platform with the Breguet spring removed. The plate lists the regulator, stud support and regulating stud as discrete parts, which is what an index-regulated caliber looks like and what a free-sprung one does not.
The higher-beat generation replaces the 1210's screwed Glucydur balance and Breguet overcoil with a smooth-rimmed balance and flat hairspring. Gilt and nickel-plated inertia blocks provide about ten seconds per day of fine adjustment across their range; the index handles larger corrections. Separate regulator, stud-support and regulating-stud parts confirm that this is an index-regulated movement, not a free-sprung one.


At auction the caliber is a near-ghost, appearing almost exclusively in the oversize ref. 8029, and the lots that do name it disagree with each other about dates. Phillips catalogued an 8029 as 1950 on Cal. 1220; Antiquorum gave case no. 714105 as circa 1951, also on Cal. 1220; Sotheby's catalogued that same case number as circa 1961 and declined to name a caliber. A 1950 date sits awkwardly with a high-beat caliber whose siblings are later-1960s work, and the record does not resolve it. The wider difficulty is that trade databases hold that 1220 movements are commonly signed 1225, which would push the caliber's real footprint — later-production Oyster Precision 6426 among them — under a number it does not wear. That signing claim could not be corroborated from an independent primary source and should be treated as unverified.
Cal. 1220 appears mainly in the oversize ref. 8029, but its dates conflict. Phillips gives 1950, Antiquorum dates case 714105 to about 1951, and Sotheby's dates that same case to about 1961 without naming its caliber. The earlier dates sit awkwardly beside the later-1960s siblings and remain unresolved. Claims that 1220 movements were commonly signed 1225, including those in later ref. 6426 production, are unverified.


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Cal. 1220 with a calendar added, carrying later-production Oysterdate Precision 6694 through the family's final years, and by a wide margin the best-documented member of the group. Its factory plate reads Ø23.80mm, 5.07mm high, train 21,600, centre second, calendar, shock proof, 17 jewels, base calibre 1210, and lists the balance as part 7625, "Balance with flat hairspring, timed," alongside a gilt and a nickel-plated inertia block. Antiquorum's cataloguing agrees from outside the factory, giving "monometallic balance, shock absorber, self-compensating flat balance-spring" for a 1972 ref. 6426 and "self-compensating steel flat balance spring" for a 1966 ref. 6694. Several caliber databases print a Breguet overcoil for the 1225 instead; the factory plate and the auction record both say flat, and this page follows them. A Bonhams lot describing a 1225 with a "Gyromax balance" is a cataloguing slip — Gyromax is Patek Philippe's free-sprung system, and no Rolex caliber uses it.
Cal. 1225 adds a calendar to the 1220 and carried the Oysterdate Precision 6694 through its final years. Rolex's plate specifies a timed flat hairspring with gilt and nickel-plated inertia blocks, consistent with Antiquorum's descriptions of refs. 6426 and 6694. Published claims of a Breguet overcoil conflict with the factory plate and auction record. Bonhams' reference to a "Gyromax balance" is a cataloguing error; Gyromax is Patek Philippe's free-sprung system.


None of the Precision calibers on this page were chronometer-certified, which is why "Precision" rather than "Superlative Chronometer Officially Certified" appears on the dial across the whole line. Michael Stockton writing for Fratello, Giovanni Di Biase at Horbiter, and published bench teardowns all state it plainly. The designation is frequently misread as meaning hand-wound, which it does not — the automatic Air-King 5500 wore "Precision" on Cal. 1520 and "Super Precision" on Cal. 1530, neither of them certified either. Some 1225 movements are also stamped "UNADJUSTED," which is an import-duty declaration rather than a grade.
None of these Precision calibers was chronometer-certified. "Precision" does not mean hand-wound: the automatic Air-King 5500 used the term with Cal. 1520 and "Super Precision" with Cal. 1530, neither certified. The "UNADJUSTED" stamp found on some 1225 movements is an import-duty declaration, not a grade.


There is no hacking. Rolex's plate for the base 1210 lists the complete keyless works — setting lever and jumper, yoke and yoke spring, setting wheel, minute wheel, cannon pinion — with no stop lever or hack spring anywhere in it, and the 1978 service book carries hack-device chapters only for the late 1500 series and the 2030/2035.
The caliber does not hack. The 1210 parts plate contains no stop lever or hack spring, and Rolex's 1978 service book covers hacking only for the late 1500 series and the 2030/2035.


The service picture is unusually well recorded for a caliber this cheap. Published teardowns put the recurring faults at the pendant tube and crown threads, the winding stem, the mainspring, and water damage to the date ring, and single out the early Oysterdate calendar construction as the weak piece of an otherwise strong movement — the same watchmaker who calls the date works improvable also describes the pallet fork as polished all over with the jewels lightly undercut, and rates the finishing a clear step above a standard ETA. The economics are the real constraint: genuine Rolex parts for these calibers now cost more than the watches, so a crown that lists at three figures gets replaced with a generic at a tenth of it, and independents charge a fraction of a factory service. Rolex's own service centres still take them on, and a 1974 example returned from a factory overhaul running two seconds a day with a measured 57-hour reserve.
Recurring service faults include worn pendant-tube and crown threads, winding stems and mainsprings, plus water-damaged date rings. The early Oysterdate calendar is the movement's weak point, though the pallet fork is fully polished and its jewels lightly undercut. Rolex service centres still accept these calibers; one 1974 example returned from overhaul running two seconds per day with a measured 57-hour reserve.


Auction lots put the caliber in refs 6426, 6466 and above all the 6694, from the later 1960s through to examples catalogued as late as 1979. A collector comparison of a 1966 6694 on Cal. 1215 against a 1973 one on Cal. 1225 places the changeover inside that reference around 1967.
Documented fitments include refs. 6426, 6466 and, most often, 6694 from the late 1960s through at least 1979. Comparison of a 1966 ref. 6694 with Cal. 1215 and a 1973 example with 1225 places the changeover around 1967.


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The small-seconds variant of the family and the thinnest of the group at 3.65mm, against 4.27mm for the sweep-seconds Cal. 1210 it is otherwise architecturally close to. Where the 1215 plate lists only its calendar parts, the 1200 gets its own main plate and its own train wheel bridge, because moving the seconds from the centre to a subdial rearranges the going train rather than adding to it. Its sheet lists a jewelled plate, jewelled train wheel bridge, centre wheel with cannon pinion, third and fourth wheels each with their own upper and lower jewels, and a jewelled pallet fork and staff, then closes by naming the nine Cal. 1210 parts the small-seconds layout does not need.
Cal. 1200 is the family's small-seconds variant and, at 3.65mm, its thinnest member. Moving the seconds from the centre to a subdial requires a separate main plate and train-wheel bridge rather than an added module. The plate, bridge, third and fourth wheels, pallet fork and staff are jewelled.


The original bilingual plate carries more of the family's mechanical detail than any other document found, because it states in Rolex's own words what the later English sheets only imply. It gives Ø23.8mm and 18,000 alternances, marks the movement with the "Rolex Shockresisting" device rather than a trade shock-protection brand, and names the balance twice: part 7535, a Glucydur balance with roller, pivoted, and part 7536, a Glucydur balance with Breguet hairspring, regulated. That is the 18,000-vph oscillator described by the manufacturer, and it is what the 1210 and 1215 inherit.
The bilingual parts plate specifies Rolex's own "Shockresisting" device rather than a trade name. It lists a pivoted Glucydur balance with roller and a regulated Glucydur balance with Breguet hairspring, the 18,000-vph oscillator inherited by the 1210 and 1215.


The same plate answers a question the caliber databases argue over. The number is engraved on the hub sinking of the balance wheel — not on a bridge, not on the mainplate — which is why the balance appears among the 1200's special parts at all when the rest of the movement is shared with the 1210. It also carries the instruction that settles the family's parentage, directing the watchmaker to the plates of calibre 1210 for everything general.
The caliber number is engraved in the balance-wheel hub sinking rather than on a bridge or the main plate. The same document directs watchmakers to Cal. 1210 for all shared parts, confirming the family's parentage.


The gap worth stating: no auction lot at any major house was found naming Cal. 1200. Everything above comes from Rolex's own documentation rather than from catalogued watches, and the references this caliber went into are not established here. Its high-beat counterpart, the small-seconds Cal. 1240 built on the 1220, is far better attested — Sotheby's, Christie's and Antiquorum all catalogue it in the platinum Cellini Cellinium 5240 and 5241, describing a monometallic balance adjusted to four positions with a self-compensating flat balance spring, which is how this architecture kept running for a decade after the Oysterdate stopped.
No major-house lot names Cal. 1200, so its fitments remain unestablished. The high-beat small-seconds Cal. 1240 is better documented in the platinum Cellinium 5240 and 5241, with a monometallic balance adjusted to four positions and a flat hairspring. That caliber kept the architecture in production for about a decade after the Oysterdate ended.


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== Vintage sport calibers (Submariner, GMT-Master, Explorer, Air-King) ==
== Vintage sport calibers (Submariner, GMT-Master, Explorer, Air-King) ==


The sport time-only and GMT line runs through three broad chapters: the A-series and Cal. 1030 opening generation above, a long 15xx-family middle chapter, and the GMT branch's own parallel thread through the bakelite-bezel era. The 15xx family anchors Rolex's longest-running production stretch — Cal. 1530 through the early 1960s, Cal. 1520 as its permanent non-chronometer twin, and Cal. 1560/1570 carrying the chronometer side of Submariner, GMT-Master, and Explorer production into the 1980s.
The vintage sport line begins with the A-series and Cal. 1030, then settles into the long-running 15xx family. Cal. 1530 served the early 1960s, Cal. 1520 became the non-chronometer mainstay, and the chronometer-grade 1560 and 1570 carried Submariner, GMT-Master and Explorer production into the 1980s.


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Rolex's first bidirectional automatic, 1950–62, 25 jewels, 18,000 vph, 42 hours, 28.5 × 5.85mm: the caliber that ends the domed-caseback era. Its "butterfly" rotor, named for its cutaway wing-like shape, is stamped ROLEX PERPETUAL PATENTED and is the single most recognizable identifier for the caliber. Straight-line lever escapement, monometallic balance adjusted to temperature and 5 positions, blued-steel self-compensating Breguet balance spring, KIF shock protection — confirmed across more than a half-dozen Antiquorum lot descriptions using near-identical wording every time. Perlage finishing on the rhodium-plated mainplate, brushed (not striped) bridges, polished screw heads, and red anodized-aluminum reversing wheels round out the finishing. Regulation runs on a traditional index rather than free-sprung Microstella, so a visible regulator arm near the balance is the fastest way to tell a 1030 apart from its free-sprung 1560/1570 successors at a glance — the free-sprung system wasn't patented until 1957, which rules it out here on dating grounds alone. It first appears on the 6098 in 1952, running through the 6536, 6536-1, and 6538 Submariners, the 6610 Explorer, and the 6552 Air-King, in both COSC and non-COSC form on the identical movement. It was Rolex's first fully in-house automatic, no external ébauche supplier, with a 5.85mm profile thin enough to leave the bubble-caseback era behind for good.
Produced from 1950 to 1962, Cal. 1030 was Rolex's first bidirectional and fully in-house automatic. Its 5.85mm profile ended the domed Bubbleback caseback, while the cutaway "butterfly" rotor stamped ROLEX PERPETUAL PATENTED is its clearest visual identifier. Finishing includes perlage on the rhodium-plated main plate, brushed bridges, polished screw heads and red anodized-aluminium reversing wheels. A conventional index regulates the movement; the visible regulator arm distinguishes it from the later free-sprung 1560 and 1570. Documented fitments include ref. 6098 from 1952, Submariners 6536, 6536-1 and 6538, Explorer 6610 and Air-King 6552. The same movement appeared in chronometer and non-chronometer watches.


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The date version of Cal. 1030, from 1957, powering the Oyster Perpetual Date 6518, 6530, and 6534 and the Datejust Thunderbird 6609. Non-quickset &mdash; Rolex's own service documentation describes its calendar mechanism as "progressive," meaning the date creeps forward gradually through the night rather than jumping instantaneously at midnight, deliberately contrasted against the 1036 GMT caliber's instant-change wording in the same table.
Cal. 1035 adds a date to the 1030 and appeared in 1957. It powered Oyster Perpetual Date refs. 6518, 6530 and 6534, plus the Datejust Thunderbird 6609. Rolex describes its non-quickset calendar as "progressive": the date moves gradually through the night, unlike the instant-change 1036 GMT.


Antiquorum's description of a 6534 sold in Geneva in November 2008 gives the mechanical spread in full: rhodium-plated, 25 jewels, straight-line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock absorber, self-compensating Breguet balance spring. A second Geneva lot from March 2008 for the same reference repeats it word for word. Neither names the regulator, and no 1035-specific description does; the Cal. 1030 base it inherits is documented with a traditional index rather than free-sprung Microstella, which is also the only reading compatible with the dates, since Rolex did not patent the free-sprung system until 1957.
The 1035 inherits the 1030's conventional index regulator rather than Microstella. Auction descriptions do not name the regulator, but the production dates and shared base support the index arrangement.


The identification problem with this caliber is genuinely awkward, and Rolex created it. The factory table records that the 1035's self-winding bridge is stamped "1030" &mdash; the movement carries its parent's number, not its own, exactly as the 1036 does. The consequence shows up immediately in the auction record: lots for a single reference come up catalogued both ways, and the 6534 in particular has been sold as a Cal. 1030 watch by one house and a Cal. 1035 watch by another, with Christie's cataloguing a 6534 under Cal. 1030 as recently as May 2024. Reading the number off the bridge cannot resolve which one is in the case. What can is the calendar work itself and the height: 6.66mm for the 1035 against 5.85mm for the plain 1030, a 0.81mm difference accounted for entirely by the date mechanism stacked on top. A 6534 is a Date reference, so the movement in a correct example is a 1035 whatever the bridge says.
Rolex stamped the 1035's self-winding bridge "1030," as it also did on the 1036. This causes auction catalogues to identify the same reference under both numbers. The calendar work and 6.66mm height distinguish the 1035 from the 5.85mm no-date 1030. A correct ref. 6534 therefore contains a 1035 regardless of its bridge engraving.


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1957–65, 18,000 vph, 44 hours, club-tooth Swiss lever escapement, screwed Glucydur balance. The 17-, 25- and 26-jewel counts are market variants available across the run rather than a progression: 17-jewel examples are confirmed in catalogue text on a 1958-era 5508, a 5500 and a 1011 Eaton, and Rolex's own 1978 service booklet still discusses 17-jewel 1520–1530 models as a live configuration two decades later.
Cal. 1530 ran from 1957 to 1965. Its 17-, 25- and 26-jewel versions are concurrent market variants, not a chronological progression. Seventeen-jewel movements appear in a 1958-era ref. 5508, a 5500 and a 1011 Eaton, and Rolex's 1978 service booklet still treats low-jewel 1520 and 1530 movements as current configurations.


The 1530 is the root of the whole 15-series. Rolex derived the 1520, 1560, 1570 and 1580 from it; they share base plates and a great many parts, and the caliber number engraved on the automatic-device bridge interchanges freely across the range, so a bridge stamped 1555 on a movement that is physically something else proves nothing about the watch. What separates them is the shape of the balance bridge and regulator. That interchangeability, and the durability that came with it, is the 1530's real contribution. It was not Rolex's first automatic, a distinction that belongs to the Cal. 1030 of 1950 and gets misassigned to the 1530 often enough to be worth stating.
Cal. 1530 is the base for the 1520, 1560, 1570 and 1580. They share plates and many service parts, including interchangeable automatic-device bridges, so the engraved bridge number may not identify the movement beneath it. Balance-bridge and regulator form are more reliable. Cal. 1030, not 1530, was Rolex's first fully in-house automatic.


Regulating it is a two-stage job. An index regulator handles coarse rate, and the balance also carries two pairs of adjustable micro-star fine-timing screws on the rim; on the 1530 and its immediate derivatives those screws sit on the outside, where turning one clockwise tightens it inward and the watch gains, while the later 3135-generation balances put the equivalent nuts on the inner rim. The Swiss tool-maker Horotec lists the same micro-star tool for the 1530 alongside the 1570, 2130, 3035, 3055, 3135 and 3155, which is good evidence the screws are a real feature and not a misreading. Rolex's own literature reserves the Micro-Stella name for the 12½′′′ chronometer calibers of 18,000 and 19,800 beat, describing those as carrying eighteen balance screws of which two are the gold star-headed regulating pair, so the 1530's screws work on the same principle without belonging to the system Rolex named. That is the ambiguity long-standing Vintage Rolex Forum contributors circle around when they compare a 1530 balance against a 1675 or 1016 and find stick regulation and a Microstella-like adjuster on the same wheel.
Regulation combines an index for coarse adjustment with two pairs of micro-star fine-adjustment screws on the outer balance rim. Turning a screw clockwise draws it inward and gains rate. The system resembles Microstella, and Horotec lists the same adjustment tool for the 1530 and later Microstella calibers, but Rolex reserved the Micro-Stella name for its free-sprung 12½-ligne chronometer movements. The 1530 retains an index.


Shock protection is KIF Flector on the form-1 balance cock, per a named UK specialist who maps cock forms 1 and 2 to Flector and forms 3 and 4 to Elastor, with two watchmakers on the NAWCC board reaching the same reading by physically comparing cocks. The caveat matters as much as the answer: because caliber-marked bridges interchange across the entire 15-series, an individual example's shock setting can differ from what its stamped number implies. That is the reason secondary sources disagree about it, rather than any of them being simply wrong.
The form-1 balance cock uses KIF Flector; forms 3 and 4 use Elastor, with form 2 also assigned to Flector by specialist comparisons. Interchangeable bridges mean an individual movement's shock setting may not match its engraved caliber number.


There is a genuine unresolved contradiction over the escapement and regulating description, and it runs between source tiers rather than within one. Antiquorum's standard formula for the 1530 reads "straight-line lever escapement, monometallic balance, shock absorber, self-compensating Breguet balance spring, index regulator," giving it an overcoil; much of the reference literature instead describes a flat hairspring with stick regulation. Both readings are in circulation from sources that are otherwise reliable, and nothing in the record resolves it.
The hairspring remains disputed. Antiquorum consistently describes a Breguet overcoil and index regulator, while much of the reference literature gives a flat hairspring with stick regulation. Reliable sources support both descriptions.


Chronometer status is murkier still, and the tidy version does not survive contact with the sources. Three major houses disagree outright: Sotheby's catalogues the 1530 as not chronometer-certified, while Phillips and Christie's both describe it as the chronometer caliber used in 5504-family watches. Collector research adds a third position, documenting rare four-line Superlative Chronometer dials on 5512 and 5508 examples running a 1530 — though no major-house lot confirms one, which makes it the weakest strand here. The safest reading is that certification was occasional rather than either routine or impossible. What is documented is the shape of Rolex's answer rather than the reason for the gap: the 1555 and 1560 were the chronometer upgrade, easier to bring to tolerance because of the Micro-Stella balance, which is why the earliest 1675 and 1016 carry them. Explanations that a cost calculation drove the omission trace to a single forum contributor who labelled the idea his own speculation, and they are not carried here.
Chronometer status also varies. Sotheby's describes the 1530 as uncertified, while Phillips and Christie's identify chronometer examples in the 5504 family. Rare 5512 and 5508 watches with four-line chronometer dials and Cal. 1530 have been reported, though no major-house lot confirms them. Certification appears to have been occasional. The Microstella-equipped 1555 and 1560 became the regular chronometer alternatives used in early refs. 1675 and 1016.


The rotor shape evolves mid-production from butterfly to half-moon, and continental auction houses name it directly, cataloguing early examples as a "rotor papillon" or "masse papillon." Later runs add blued screws on the auto-winding bridge — Rolex's own strip-down instructions open by calling for "the three blue screws of the automatic bridge" — with coloured reversing wheels replacing the original brass-coloured gears. Collectors describe those wheels as purple and Teflon-coated; Rolex describes the red finish as a surface treatment applied to aluminium for hardness and dates its introduction to 1957, the 1530's own first year. Either way, both are genuine dating markers for a given example.
The rotor changed from butterfly to half-moon during production. Later movements also gained blued automatic-bridge screws and coloured reversing wheels in place of brass-coloured gears. Rolex describes the red wheel finish as a hardening treatment for aluminium introduced in 1957; collector descriptions often call the wheels purple and Teflon-coated. Rotor and reversing-wheel form help date an example.


First Submariner appearance is the 5508, with the 5510 following months later, and neither was chronometer-rated at launch. The wider pattern is that the 1530 came in as the replacement for the 10-series in Rolex's non-chronometer watches — the 6536 becomes the 5508, the 6538 becomes the 5510 — arriving alongside new Precision models, the Air-King, the 5504 "Super-Precision" Explorer and the Canadian-market Explorer-Date with its Cal. 1535. It did not immediately displace the older calibers where certification mattered: the 6542 GMT, the 6610 Explorer, and the Datejust and Day-Date lines all held onto their 10xx movements for a while yet. Multi-house lots confirm the 1530 in the 5508, 5510, 5512, 5513, 5500 and 5504, with thinner single-lot support for the 5501, 5502, 5506, 5516 and the 5590/1011 Eaton. Two Bonhams online-tier lots catalogue a 1002 and a 1003 as Cal. 1530 against the Watch-Wiki concordance that assigns it to the 5500 family only, but both carry internal inconsistencies and no other house corroborates them — a shaky outlier rather than a confirmed fitment.
The 1530 first entered the Submariner in ref. 5508, followed by 5510; neither was chronometer-rated at launch. It replaced the 10-series in non-chronometer watches, including Precision models, the Air-King, ref. 5504 "Super-Precision" Explorer and the Canadian Explorer-Date with Cal. 1535. Certified models such as the 6542 GMT, 6610 Explorer, Datejust and Day-Date retained 10xx calibers for longer. Strongly documented fitments include refs. 5508, 5510, 5512, 5513, 5500 and 5504. Single-lot support exists for 5501, 5502, 5506, 5516 and 5590/1011 Eaton. Bonhams listings for refs. 1002 and 1003 are internally inconsistent and remain unconfirmed.


Three service details are worth carrying, all of them factory-documented. Rolex specifies mainspring strength of 0.122 to 0.125mm for the 18,000-beat 1530 and 1560, against up to 0.125 or 0.128mm for the 19,800-beat 1520 and 1570, which is worth knowing on any movement rebuilt with whatever was on the bench. The unjewelled barrel bridge and arbor hole wear in early production, and Rolex's instructions cover both closing the hole and reaming it for a jewel; later production got a bushing that largely ended it, and rotor-axle wear on the winding weight is the companion complaint. And the family's known defect sits one caliber over: hard jarring could throw a 1560's hairspring out far enough to catch the regulator, which Rolex fixed with a safety pin supplied free of charge from its Material Division and made standard partway through production, so some carry it and some do not. The factory booklet devotes a page to those hairspring guards, which is about as clear an admission of a recurring fault as Rolex ever put in print.
Rolex specifies a 0.122–0.125mm mainspring for the 18,000-vph 1530 and 1560, against up to 0.125 or 0.128mm for the higher-beat 1520 and 1570. Early unjewelled barrel-bridge arbor holes can wear; Rolex prescribed closing the hole or reaming it for a jewel, while later production received a bushing. Rotor-axle wear is another known fault. On the 1560, a hard shock could push the hairspring into the regulator. Rolex supplied a safety pin free of charge and later made it standard, so both guarded and unguarded examples are correct.


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1963–90, 17/25/26 jewels at 19,800 vph, the non-chronometer member of the higher-beat pair. Rolex's own factory parts plate heads the caliber "Base Calibre 1530," which is the accurate lineage: the 1520 is a 1530 derivative that took over at the faster rate. The pairing worth remembering is by beat, not by name. Rolex's service literature sets 1530 against 1560 at 18,000 vph and 1520 against 1570 at 19,800 vph, so the 1520's certified counterpart is the 1570, not the 1530 it descends from.
Produced from 1963 to 1990, Cal. 1520 is the non-chronometer, higher-beat derivative of the 1530. Rolex pairs the 18,000-vph 1530 with the 1560, and the 19,800-vph 1520 with its certified counterpart, the 1570.


That same literature is unusually direct about how the thing is regulated. The factory booklet lists it as "12½′′′ round, self-winding, 19,800 beat, regulation by regulator and inertia blocks," and sets it against the Cal. 1570 on the same page, regulated "by Micro-Stella systems." The 1520's balance is screwless and its hairspring flat; two inertia blocks, one gilt and one nickel (parts 8056-1 and 8056-2), sit on the balance rim and are turned with a hairspring-collet blade. Directing their splits toward the centre of the wheel slows the watch and turning them outward gains time, with roughly ten seconds a day of correction available from one extreme to the other. Coarse rate comes from the regulator. Note that this is not the 1530's arrangement: that caliber trims with micro-star screws, and the two systems are often conflated.
Rolex describes regulation by an index and two inertia blocks, one gilt and one nickel-plated, on a screwless balance with a flat hairspring. Turning their splits inward slows the movement and outward gains rate, with about ten seconds per day across the adjustment range. The index handles coarse changes. This differs from both the 1530's micro-star screws and the 1570's free-sprung Microstella system.


What actually sorts the certified calibers from the uncertified ones across this family is the regulating system, not the hairspring. Rolex states that Micro-Stella is used in all 12½′′′ Rolex chronometers of 18,000 and 19,800 beat, and describes the 1520's screwless balance, flat hairspring, regulator and inertia blocks as the alternative arrangement. The flat hairspring is well documented — seven independent Antiquorum lot descriptions carry it — but it did not by itself keep the caliber out of certification, since the 1530 has a Breguet overcoil and went mostly uncertified too. Free-sprung Micro-Stella regulation is what correlates.
The regulating system, rather than hairspring form, separates the certified calibers from the rest of this family. Rolex used free-sprung Microstella regulation in its 12½-ligne chronometers, while the 1520 retained an index and inertia blocks.


The arrangement gets misread constantly, because eccentric weights on a balance rim look like a free-sprung system. Watchmakers on the NAWCC message board have argued in circles over whether a 1520 even has a regulator, one contributor concluding after comparing examples that they turn up "some with regulators, some without, some with the eccentric weights, some without, but none with the microstella screws." The auction record repeats the confusion in a more damaging form: two Bonhams lots describe a 26-jewel 1520 as having a "free-sprung Gyromax balance," a Patek Philippe trademark attached to a movement that is neither free-sprung nor Patek's.
The rim weights can be mistaken for a free-sprung system, but factory documentation confirms the regulator and inertia blocks. Two Bonhams descriptions call the 1520's balance "free-sprung Gyromax," an error that applies Patek Philippe's trademark to an index-regulated Rolex movement.


Antiquorum's house wording is the dependable one and it holds across lots spanning twenty years: "straight-line lever escapement, monometallic balance, shock-absorber, self-compensating flat balance-spring." One Antiquorum lot from 2013 says "Breguet" where every other lot from the same house says flat, and it reads as boilerplate slippage. Shock protection is real but never named in a catalogue; houses write "shock-absorber" or "antichoc" and stop. A specialist repairer's identification guide covering the 1520 to 1580 range attributes the series to KIF in Flector and Elastor patterns, assigned by which of four balance-bridge-and-regulator forms a movement carries, and makes the useful point that the bridge shape rather than the caliber number engraved on it is what identifies these movements, since the numbered bridge interchanges across the whole series.
Auction descriptions consistently give a flat hairspring, apart from one 2013 Antiquorum outlier that says Breguet. Shock protection is KIF in Flector or Elastor form, identified by balance-bridge and regulator shape. That shape is more reliable than the engraved caliber number because bridges interchange across the series.


The 17-, 25- and 26-jewel counts are market variants, not a chronology, and the jewels are not where people assume. Rolex's own parts numbering shows the 17-jewel version using a different main plate, different bridges, different escape-wheel pivot geometry and bushings in place of jewels in the automatic module — so it is a physically different movement, but the differences are confined to the winding module and escape wheel and never touch the going train or the balance, which is why jewel count has no bearing on timekeeping. Dated lots put 17-jewel movements between 1965 and 1970 and 26-jewel movements inside that same window and earlier: a 26-jewel 5513 at case 1'293'711 sits about 22,000 serials from the 17-jewel Sealab III 5513. A 25-jewel tier runs alongside both, on a 9ct 5500 with a 1967 London import mark and a 1973 Pan Am 5500.
The 17-, 25- and 26-jewel counts are concurrent market variants. The 17-jewel version uses a different main plate and bridges, altered escape-wheel pivot geometry, and bushings in place of jewels in the automatic module. The going train and balance are unchanged, so jewel count does not affect timekeeping. Dated examples place 17- and 26-jewel movements together from the mid-1960s, with 25-jewel examples running alongside them.


The tariff explanation deserves care in both directions. The bracket itself is real and citable: the Tariff Schedules of the United States broke sharply above 17 jewels, taxing higher-count movements at a steep premium over the low-jewel rate. Whether that specifically drove Rolex's choice is undocumented, and the best forum research argues against the simple reading — one long-standing contributor reports 17-jewel movements going to Europe and Asia as well as the United States, and reads the change as general cost-cutting from the mid-1960s rather than US-market targeting. No auction catalogue states a reason at all. The American corporate-presentation reference 7002 does carry a 1520 rotor stamped "SEVENTEEN JEWELS" and "UN" for unadjusted, the two declarations the US schedules keyed on, which is suggestive without settling it.
American tariffs rose sharply above 17 jewels, but Rolex did not document this as the reason for the low-jewel version. Seventeen-jewel movements also reached Europe and Asia, so general cost reduction remains another possibility. The American presentation ref. 7002 has a rotor marked "SEVENTEEN JEWELS" and "UN" for unadjusted, both relevant to the tariff schedule, but this does not settle the question.


Fitment is better documented than for most vintage calibers, and one common attribution is wrong. Major-house lots confirm the 1520 in the 5513 across case numbers from roughly 1.29 million to 8.46 million, in the 5514 COMEX, in the 5517 military Submariner, in the 5500 Air-King and in the 5520, the last unusually well, since the same 1983 watch, case 7'473'941, was catalogued as a 26-jewel 1520 by Antiquorum in 2006 and again by Christie's in 2008. The 1002 Oyster Perpetual does not belong on that list: every apparent "1002 with a 1520" turns out to be a 5500 case with 1002 stamped inside the caseback, while lots for an actual 1002 run chronometer calibers, 1530 or 1570. The 5501 sits in the same doubtful column, appearing with a 1520 in dealer listings but not in any major-house lot. Hacking arrives as a running change around 1972, via parts 8073 and 8074 and the factory section on the hack device for late 1500-series movements, and it dates an example usefully. There is also a dial tell for the non-chronometer status: a 1520 watch carries two lines of text above six o'clock rather than the four a chronometer-certified movement earns, a point Sotheby's makes explicitly, and Phillips describes early 5513s as carrying the 1530 and later ones the "non-chronometer cal. 1520."
Documented fitments include the 5513, 5514 COMEX, 5517 military Submariner, 5500 Air-King and 5520. Ref. 1002 uses chronometer calibers 1530 or 1570; apparent 1520 examples are ref. 5500 cases with 1002 stamped inside the caseback. Ref. 5501 remains unconfirmed. Hacking arrived as a running change around 1972 through parts 8073 and 8074. Two lines above six o'clock identify the non-chronometer dial, against four on certified models.


On service, Rolex's instructions for the series single out the barrel bridge and barrel arbor hole as the wear point, with directions for closing a worn hole or reaming it to take a 2.30mm jewel; later production got a beryllium bushing that largely ended the problem. Rotor-axle wear is the other documented item, and independent watchmakers add worn autowinder wheels, with the difficulty that Rolex no longer supplies parts. One symptom that is not a fault: gritty or grainy manual winding is normal on a 1520, because the reversers are designed to run unlubricated.
The barrel bridge and arbor hole are known wear points. Rolex prescribed closing a worn hole or reaming it for a 2.30mm jewel; a later beryllium bushing largely solved the problem. Rotor axles and autowinder wheels also wear, and replacement parts are scarce. Gritty manual winding is normal because the reversers run without lubrication.


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A date-module variant of Cal. 1530, from 1957, non-chronometer, powering the 5700/5701 Air-King-Date. That attribution rests on two things, neither of them an auction catalogue. Rolex's own factory caliber table, in Mark Sirianni's transcription, places 1535 as the earlier, 1530-based date module and 1525 as the later, 1520-based one below — a reading the dates themselves require, since a movement derived from Cal. 1520 cannot predate 1520's own 1963 introduction. Editorial coverage of the line agrees: Erik Slaven's history of the Air-King for Monochrome, January 2025, gives the 5700 calibre 1535 with some examples on 1525, both Precision grade rather than chronometer.
Cal. 1535 is the non-chronometer date version of the 1530, introduced in 1957 for the Air-King-Date 5700/5701. Rolex's factory caliber table places it before the later 1520-based Cal. 1525, consistent with the production dates. Monochrome likewise assigns both calibers to the 5700, with 1535 first.


No auction lot names this caliber. Across Antiquorum, Sotheby's, Phillips and Bonhams, the 5700 and 5701 lots that should carry a 1535 are catalogued under the base caliber instead — Antiquorum gave a 1963 Explorer-Date 5700 as Cal. 1530, in Revolution: The Evolution of the Rolex Sport Watch, New York, 17 April 2008, lot 93, and a 1972 example of the same reference as Cal. 1520, in New York on 11 December 2008, lot 71. Neither reading works literally, because neither base caliber carries any date work at all. Taken as house shorthand for the family rather than the exact variant, the two lots line up with the order the factory table gives: earlier watch on the earlier base, later watch on the later base. Rolex's parts catalogues group the date variants the same way, filing 1535 components against the 1530 and 1525 against the 1520. That is corroboration of the lineage, not confirmation of the caliber number, and the distinction is worth holding onto.
Auction houses usually catalogue refs. 5700 and 5701 under the base caliber. Antiquorum assigns a 1963 ref. 5700 to Cal. 1530 and a 1972 example to 1520, though neither base movement has a date. Read as family shorthand, those entries match Rolex's parts catalogues, which file 1535 components with the 1530 and 1525 components with the 1520. They support the lineage but do not confirm the exact caliber number.


Every mechanical figure in the table above is read across from the 1530 base rather than observed on a movement catalogued as a 1535. Those 1530 lot descriptions give rhodium plating, 26 jewels, straight-line lever escapement, monometallic balance, self-compensating flat balance spring. The flat spring cuts against the parts evidence. Rolex balance assembly 7855, the one specified for the 1530, carries a Breguet overcoil; the flat spring belongs to assembly 8055 and the 1520. Both readings sit in the record, and boilerplate is the likelier explanation than a variant, since the same house prints near-identical movement wording across the whole 1500 family. What is not in dispute is that the 1530 predates Microstella. Rolex introduced those screws on the 1565 in 1959, two years into 1530 production, so a 1535 regulates at an index against a screwed balance — the arrangement Rolex found too slow to certify at volume, which is much of why the 5700 was sold as a Precision rather than a chronometer.
The table's mechanical figures derive from the 1530 base because no auction lot identifies a 1535 directly. Evidence for the hairspring conflicts: auction wording gives a flat spring, while Rolex balance assembly 7855 for the 1530 uses a Breguet overcoil. Repeated catalogue boilerplate is more likely than a separate variant. The 1535 predates Microstella and uses an index with a screwed balance, consistent with the 5700's Precision grade.


Cal. 1530 is the root of the whole 1500 family, in production from 1957 and phased out by 1965 as the 1560, 1570 and 1520 divided the range between them at different price points. The 1535 outlived its own base by decades inside the 5700, which is how a late-1980s Air-King-Date ends up carrying a movement whose design predates the Submariner's crown guards.
Although Cal. 1530 was phased out by 1965, its 1535 date derivative remained in the Air-King-Date into the late 1980s.


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A date-module variant of Cal. 1520, from 1965, non-chronometer, carrying the 5700/5701 Air-King-Date through its later production years — the higher-beat 19,800 vph sibling of Cal. 1535 above. The chronometer-rated date option in this generation runs on a related 1500-series caliber instead, in the 1500/1501/1503/1505 Oyster Perpetual Date.
Cal. 1525 is the higher-beat, non-chronometer date version of the 1520. Introduced in 1965, it carried the Air-King-Date 5700/5701 through later production. Contemporary chronometer-rated Oyster Perpetual Date references used a related 1500-series caliber instead.


Antiquorum catalogued a 5700 Explorer-Date made in 1972 as Cal. 1520 rather than 1525 — rhodium-plated, 26 jewels, straight-line lever escapement, monometallic balance, shock absorber, self-compensating flat balance spring, in New York on 11 December 2008, lot 71. That base-caliber habit runs through the house's 5700 lots, and it is why the auction record is a poor place to go looking for the number 1525 itself: the date function is a module, and the catalogue describes the movement underneath it. What the record does establish is the architecture, and it is the cost-controlled end of the 1500 family. The flat balance spring is the tell. The chronometer-grade members of the same generation, the 1560 and 1570, carry a Breguet overcoil, and the absence of one here is the mechanical reason a 5700 dial reads Precision rather than Superlative Chronometer.
Auction catalogues often identify this movement by its 1520 base rather than the 1525 date variant. Antiquorum does so on a 1972 ref. 5700, while describing the expected flat hairspring and index-regulated architecture. The chronometer-grade 1560 and 1570 use a Breguet overcoil and Microstella; the 1525's simpler regulating organ suits the 5700's Precision grade.


Jewel counts move around in the record — 17 and 25 in caliber listings, 26 in the Antiquorum lot descriptions — which is normal for a movement built in parallel executions for different markets and not evidence of a variant. The regulating system is settled by Rolex's own balance-assembly part numbers. The 1520 takes assembly 8055 with a flat hairspring, against 7855 with a Breguet spring on the 1530 and 7980 with Microstella screws on the 1560. Microstella entered the 1500 family with the 1565 in 1959 and never reached the 1520 or the 1525, so rate on this pair is set at an index rather than on the balance rim.
Jewel counts of 17, 25 and 26 reflect parallel market executions rather than separate variants. Rolex balance-assembly numbers confirm a flat hairspring for the 1520 and 1525, against a Breguet spring on the 1530 and Microstella on the 1560. The 1525 remains index-regulated.


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Cal. 1560 arrived in 1959 as the chronometer-grade build of the 15xx platform, and Antiquorum's standard cataloguing formula describes it better than any spec sheet. From its New York sale of 12 June 2012, lot 71, a ref 1502/1503 of about 1961: "M. Cal. 1560, rhodium-plated, 26 jewels, straight-line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock absorber, self-compensating freesprung flat balance spring, Microstella regulating screws." The four-line 5512 the same house sold on 25 April 2012 repeats the 26-jewel count; its Geneva sale of 16 March 2008 contradicts it with "Cal. 1560, rhodium-plated, oeil-de-perdrix decoration, 25 jewels." Both counts sit in the auction record unreconciled. The 1502 description's "flat balance spring" is an outlier of its own — nearly every other 1560 lot from the same house reads Breguet at that point in the formula.
Cal. 1560 arrived in 1959 as the chronometer-grade 15xx movement, with a free-sprung balance adjusted to temperature and five positions. Auction catalogues give both 25 and 26 jewels without establishing a pattern. Antiquorum usually describes a Breguet overcoil; its flat-hairspring description for one ref. 1502/1503 is an outlier.


What separates the 1560 from the 1530 is the regulating organ rather than the jewel count. Free-sprung balance, Microstella regulating screws, no index: the Vintage Rolex Forum specialist posting as tomvox1 argued in his April 2011 thread on the 1530 that this is what made the platform submittable at all, since "it was not until the development of Micro-Stella regulation that the consistency required for the rigorous Chronometer tests could be achieved on the new 15xx platform." The certification wording needs care. COSC was not founded until September 1973, so a 1959–65 movement was tested by the older Bureaux Officiels de Contrôle de la Marche des Montres, usually under a collective certificate, against a standard closer to −1/+10 seconds a day in five positions than the −4/+6 that arrived with COSC. Accounts crediting the 1560 with a COSC certificate are back-dating an institution.
Microstella regulation, rather than jewel count, separates the 1560 from the 1530. Its free-sprung balance has no index. Watches made from 1959 to 1965 were tested by the Bureaux Officiels de Contrôle de la Marche des Montres, usually under collective certificates and to a standard around −1/+10 seconds per day in five positions. COSC did not exist until September 1973, so describing an early 1560 as COSC-certified is anachronistic.


Rolex's parts numbering pins the balance down. The balance complete for the 18,000 vph chronometer group — 1555, 1556, 1560, 1565 — is part 7980, packaged under the full factory designation 1555-7980. Its 19,800 vph replacement, part 8106, is packaged as fitting 1556, 1560, 1565, 1565G, 1570, 1575, 1575G and 1575GMT alike, which is how a serviced 1560 can come back running a later balance; the balance bridge, 8102, spans the family the same way. Documented fitments are the four-line 5512, the 5504, and the 1016 Explorer, one 1964 example of which Antiquorum catalogued as "M. Cal. 1560, rhodium-plated, 26 jewels." The GMT-Master 1675 is not among them, and the reason it is listed as one constantly is an engraving habit: Rolex stamped bridges for a whole caliber family instead of numbering each variant, so a 1565 or 1575 carrying a date and a 24-hour hand still reads 1560 or 1570 on the bridge. Sotheby's catalogued an eagle-beak 1675 in London in 2019 as "cal. 1560 automatic, 25 jewels," and Monochrome states the practice outright — Rolex "used engraved plates for an entire family of movements instead of individualising calibre numbers." The 1675 ran the 1565 to roughly the 1.4-million serial range and the 1575 after it. A base 1560 has neither the calendar work nor the 24-hour train to run one. The end of the caliber's own run is softer than the usual 1965 cutoff, too: the 1570 took over as the new fitment that year, but Monochrome's Explorer history has the 1560 still turning up in watches "until around 1967."
Factory balance 7980 serves the 18,000-vph chronometer group: 1555, 1556, 1560 and 1565. Later replacement part 8106 and balance bridge 8102 span both 18,000- and 19,800-vph family members, so a serviced 1560 may carry the later balance. Documented fitments include the four-line 5512, 5504 and Explorer 1016. The GMT-Master 1675 instead used the 1565 to about the 1.4-million serial range and the 1575 thereafter. Family-wide bridge engravings explain 1675 movements marked 1560 or 1570; a base 1560 lacks both calendar and 24-hour works. Although 1570 became the new fitment in 1965, 1560 movements appear in Explorers until about 1967.


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1959–65, 25 or 26 jewels depending on source, 18,000 vph, 44 hours, the "caller" GMT caliber in the early 1675 — 24-hour hand still linked to the main hour hand rather than jumping independently, the layout the whole GMT branch carries until Cal. 3085 breaks the pattern decades later. Antiquorum's own cataloguing of a 1675 names it directly and marks the regulating-organ transition this caliber represents: monometallic balance, KIF shock protection, and — for the first time in this lineage — a free-sprung self-compensating Breguet spring with Microstella regulating screws in place of the index regulator every earlier sport caliber on this page uses, consistent with Rolex's free-sprung system reaching production only after its 1957 patent.
Produced from 1959 to 1965, Cal. 1565 is the early ref. 1675's "caller" GMT movement: its 24-hour hand remains linked to the main hour hand rather than independently adjustable. Rolex kept that layout until Cal. 3085. The 1565 introduced a free-sprung Breguet overcoil with Microstella regulation to this lineage, replacing the index used by earlier sport calibers.


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Cal. 1570 is the 19,800 vph revision of the 1560, introduced in 1965. The fullest published description of one comes from Antiquorum's Geneva sale of 14 May 2017, lot 544, a 1967 ref 1665 single-red Sea-Dweller: "Cal. 1570, rhodium-plated, oeil de perdrix decoration, 26 jewels, straight-line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock absorber, self-compensating free-sprung Breguet balance spring, Microstella regulating screws." That lot also shows the trap in reading the auction record as a caliber census: the 1665 has a date, so the movement inside it is a 1575 wearing a bridge Rolex engraved 1570. The escapement, balance and regulation described are the family's. The caliber number is packaging.
Cal. 1570 is the 19,800-vph revision of the 1560, introduced in 1965. It retains the free-sprung Breguet overcoil and Microstella regulation, with adjustment to temperature and five positions. Family-wide bridge engraving causes date movements such as the 1575 in a ref. 1665 to appear marked 1570; the engraving alone does not identify the exact caliber.


The regulating screws are the detail most often miscounted. There are four, not two, in two sizes, adjusted in opposing pairs — Rolex's own instructions for the Microstella wrench, tool part 2019, listed for calibers 1570, 3035, 3135 and 4130, put it plainly: "It is essential that the adjustment of a pair of Microstella nuts, short or long, be identical, so as not to modify the balance wheel poising." Rolex sold the screws in factory lots of four covering the 1560, 1565, 1570 and 1575. The larger pair shifts the rate by roughly two seconds a day, the smaller by about one. The two generations differ in where the hardware sits: this family carries timing screws set into the balance rim, where the 3135 platform carries four Microstella nuts on the inner rim.
The balance has four Microstella screws in two opposing pairs, not two. Rolex required equal adjustment within each pair to preserve poise. The larger pair changes rate by about two seconds per day and the smaller by about one. On this family the screws sit in the balance rim; the later 3135 platform moves its Microstella nuts to the inner rim.


Shock protection is habitually given as Kif Ultraflex, and the primary document says otherwise. KIF's own spare-material catalogue of about 1972, scanned and posted to the NAWCC message board in December 2018, lists two settings against Rolex — Ref. 2 Flector and Ref. 3 Elastor. Ultraflex is that catalogue's Ref. 6 and does not appear among the Rolex options at all. Auction catalogues record only "shock absorber" and never name a pattern, and Rolex's part number for the upper balance setting, 8065, is shared across the 1520, 1530, 1560 and 1570 without distinguishing one. KIF, then, Flector or Elastor if pressed, and Ultraflex looks like a guess that propagated.
KIF's circa-1972 material catalogue lists Flector and Elastor settings for Rolex, not Ultraflex. Auction catalogues name only a shock absorber, while Rolex part 8065 serves the upper balance setting across the 1520, 1530, 1560 and 1570. Flector and Elastor are therefore the supported patterns.


Hacking arrived mid-run and the year is genuinely disputed. Monochrome's Explorer history gives 1971, its Datejust history 1972, and RolexForums contributors who have handled the range argue there was no single date at all: "It wasn't an across the board switch on a certain day in all models at the same time." 1971–72 is best read as a phased window varying by model. The run is longer than the usual 1965–80 shorthand, too — Cal. 3035 took over new production from 1977, but the 1016 Explorer kept the 1570 until that reference ended in 1988–89. On dimensions, 12.5 lignes is the citable figure and converts to 28.2mm; the 28.5mm in wide circulation is a rounding of the same measurement rather than an independent one, and published movement heights vary enough to be worth ignoring.
Hacking appeared gradually around 1971–72, with timing varying by model. Cal. 3035 began replacing the 1570 in new production from 1977, but the Explorer 1016 retained it until 1988–89. The documented diameter is 12.5 lignes, or 28.2mm; the often-published 28.5mm is a rounded conversion. Published heights conflict.


<span id="cal-1575"></span>
<span id="cal-1575"></span>
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Cal. 1575 is the 1570 with calendar work, and in its GMT execution with a 24-hour train as well. Antiquorum's Mondani Collection sale in Geneva on 14 May 2006, lot 255 — a 1970 ref 1680 "Red" Submariner that took CHF 20,060 — gives the full description: "M. Cal. 1575 rhodium-plated, 'oeil-de-perdrix' decoration, 26 jewels, straight line lever escapement, monometallic balance adjusted to temperatures and 5 positions, self-compensating free-sprung Breguet balance-spring, Microstella regulating screws." Sotheby's gives the same 26 jewels for a 1655 Explorer II, and Antiquorum catalogues that reference's movement as "M. Cal. 1575 GMT ... 26 jewels." Against the houses, watchmaker Ashton Tracy's 2018 study of the caliber for ''Quill & Pad'' lists 25. Power reserve is 48 hours on Tracy's figures; no source found publishes the 50 hours the caliber is often credited with.
Cal. 1575 adds calendar work to the 1570; the GMT execution also adds a 24-hour train. Antiquorum and Sotheby's give 26 jewels, while watchmaker Ashton Tracy's 2018 ''Quill & Pad'' study gives 25. Tracy records a 48-hour power reserve; the often-published 50-hour figure lacks support.


The Mondani lot also carries the note that settles most of the confusion around this movement: "Caliber 1575 is an improved version of the caliber 1570. The bridge of the caliber 1575 is however still engraved 1570. For the technical details see the Rolex Oyster Catalogue, R20." An owner reading 1570 through the caseback of a 1680 or a 1675 is looking at a family engraving, not an identification. Rolex's parts naming is finer than the collector shorthand as well: the factory distinguishes 1565G, 1575, 1575G and 1575GMT, so date and GMT are separately catalogued builds rather than two interchangeable modules on one caliber. The GMT components carry their own numbers — calendar wheel 8034, cam yoke 8006, centre wheel with cannon pinion 8030, hour wheel 8040 — and circulated as a conversion set from a standard 1560 or 1570. The houses follow Rolex's naming, which is why the 1655 catalogues as a 1575 GMT.
Rolex engraved the 1575 bridge "1570," so that marking on a ref. 1680 or 1675 identifies the family rather than the exact caliber. Factory parts records distinguish 1565G, 1575, 1575G and 1575GMT. Date and GMT versions are separately catalogued builds, and the GMT parts also circulated as a conversion set for a standard 1560 or 1570.


The balance is the 1570's, and the parts numbering proves it rather than asserting it: factory balance complete 8106 is packaged as fitting 1556, 1560, 1565, 1565G, 1570, 1575, 1575G and 1575GMT alike. Tracy flags one feature unusual for the period — shock protection on the escape wheel, dial side and movement side both, not on the balance alone. Documented fitments are the 1680 date Submariner, the 1675 GMT-Master from roughly the 1.4-million serial range, the 1655 Explorer II, and the 1665 Sea-Dweller.
The 1575 shares factory balance assembly 8106 with the 1570 and related family members. It also has escape-wheel shock protection on both dial and movement sides, not only on the balance. Documented fitments include the Submariner 1680, GMT-Master 1675 from about the 1.4-million serial range, Explorer II 1655 and Sea-Dweller 1665.


<span id="gmt-branch"></span>
<span id="gmt-branch"></span>
== GMT-Master line ==
== GMT-Master line ==


The GMT branch reads in three distinct steps rather than a single continuous upgrade path. Cal. 1036 and 1065 belong to the bakelite-bezel 6542 era and keep the 24-hour hand synchronized to the main hour hand. Cal. 1565, 1575, and 3075 carry that same synchronized "caller" layout through the 1675 and 16750 generation. Cal. 3085 then breaks the pattern with the GMT branch's first independently jumping local hour hand, and Cal. 3175 keeps the older synchronized layout alive in parallel on the 16700 until 1999 even as Cal. 3185 and 3186 define the long 16710 run that follows.
The GMT branch developed in three steps. Cal. 1036 and 1065 belong to the bakelite-bezel 6542 era, with the 24-hour hand synchronized to the main hour hand. Cal. 1565, 1575, and 3075 retained that "caller" layout through the 1675 and 16750 generations. Cal. 3085 introduced the independently jumping local hour hand, while Cal. 3175 kept the synchronized layout in the 16700 until 1999 alongside the Cal. 3185 and 3186 used in the 16710.


<span id="cal-1036"></span>
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Cal. 1036 is Rolex's first GMT movement, the Cal. 1030 with a 24-hour train added for the bakelite-bezel 6542. Ashton Tracy's 2018 piece on the reference for ''Quill & Pad'' gives the movement as "automatic Caliber 1036; 2.5 Hz/18,000 vph frequency, chronometer certified," and Hodinkee's Reference Points survey of the line fixes the sequence: across the 6542's five years "from 1955 through 1959," the reference "used a 38mm Oyster case and three different automatic GMT-Master movements. First, there was the cal. 1036, then the 1065, and finally the 1066." The certification is worth reading the way the 1560 entry above sets out — a 1950s chronometer certificate came from the Bureaux Officiels, not from COSC, which did not exist until 1973, whatever a modern catalogue entry calls the accompanying paper.
Cal. 1036 is Rolex's first GMT movement, a Cal. 1030 with a 24-hour train added for the bakelite-bezel 6542. It runs at 18,000 vph and was chronometer certified. The 6542 used Cal. 1036 first, followed by 1065 and 1066 during its 1955&ndash;1959 production run. Its period chronometer certificate came from the Bureaux Officiels; COSC did not exist until 1973.


The start year is contested and the disagreement is worth keeping rather than resolving. Phillips catalogues 6542 lots with the line that the reference was "first released in 1954"; Hodinkee dates production from 1955; and Rolex registered the GMT-Master name on 21 April 1955. A watch designed and announced in 1954 and sold from 1955 fits every version of the record.
The start year remains disputed. Phillips dates the 6542's release to 1954, Hodinkee starts production in 1955, and Rolex registered the GMT-Master name on 21 April 1955. An announcement in 1954 followed by sales in 1955 would reconcile those dates, but Rolex has not documented that sequence.


Below the caliber number the record thins out badly, which is why three rows of the table above are marked inferred. Phillips's standard 6542 movement line stops at "Automatic, cal. 1065, 25 jewels" — no escapement, no balance, no shock protection — and Antiquorum's caliber index returns no Rolex 1036 lots at all. The escapement, balance and shock figures here are therefore read across from the Cal. 1030 base rather than observed on a 1036, and they should be treated that way until a lot description or a factory document says otherwise. The near-total absence of the number from the auction record is itself the notable thing: houses catalogue 6542s as 1065 and 1066 repeatedly and as 1036 almost never.
The escapement, balance, and shock protection in the table are inherited from the Cal. 1030 base rather than documented on a Cal. 1036. Auction catalogues seldom identify a 6542 movement as Cal. 1036, so those three specifications remain provisional.


<span id="cal-1065"></span>
<span id="cal-1065"></span>
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Cal. 1065 is the mid-run 6542 caliber, and unlike the 1036 it is well represented in the auction record. Phillips catalogues it in the same terse formula across at least four sales — "Automatic, cal. 1065, 25 jewels" — on the Serpico y Laino-signed gold 6542 in its Double Signed sale, on the gold example in The Geneva Watch Auction: THREE, on lot 952 of The Hong Kong Watch Auction: SIX, and on lot 10 of the New York STYLED sale of 2018. Twenty-five jewels is consistent across all of them, as it is across the house's lots for the Cal. 1066 that followed.
Cal. 1065 is the mid-run 6542 caliber. Multiple Phillips lots identify it as an automatic movement with 25 jewels, the same jewel count recorded for the Cal. 1066 that followed.


The dates are softer than the specification. Hodinkee's Reference Points survey places the 1065 second in the 6542's three-caliber sequence without attaching a year, and the figure in general circulation is 1957; nothing found — no lot, no Rolex document — fixes it more tightly than the back half of the reference's run. The same caution applies to the 42-hour power reserve in the table, which is the consistent secondary figure rather than a documented one.
Its dates are less secure than its specification. Cal. 1065 sits second in the 6542's three-movement sequence and is generally dated to 1957, but no factory document or dated lot fixes the transition. The 42-hour power reserve is also a secondary-source figure.


The escapement, balance and shock rows are inference for the same reason they are on the 1036: Phillips stops at caliber and jewel count, so the mechanical description is read across from the Cal. 1030 base these GMT calibers were built on. The Cal. 1066 entry below can make that read-across directly, since Antiquorum's 1066 lots reproduce the 1030 formula word for word. The 1065 has to borrow it.
The escapement, balance, and shock rows likewise derive from the Cal. 1030 base. Cal. 1066 cataloguing supports that family relationship, but these details have not been documented directly on a Cal. 1065.


<span id="cal-1066"></span>
<span id="cal-1066"></span>
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1957–59, 25 jewels, 18,000 vph, 42 hours — the third and final movement Rolex fitted to the 6542 across its five-year run, replacing Cal. 1065 for the last two years of production. Antiquorum's catalogue formula for it reads "Cal. 1066, rhodium-plated, 25 jewels, straight-line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock absorber, self-compensating Breguet balance spring," printed in those words on a 1959 steel example sold in New York in December 2009. The same house applies the identical sentence to the plain Cal. 1030 on earlier 6542s, and to the Cal. 1065 on a gold example sold in New York in April 2008. That shared text is the strongest evidence that all three sit on one base with a GMT module added, and it upgrades the 1065's inheritance from inference to something the catalogue record actually states.
Cal. 1066 was the third and final movement fitted to the 6542, replacing Cal. 1065 for the last two years of production. It runs at 18,000 vph with 25 jewels and about 42 hours of reserve. Antiquorum describes a straight-line lever escapement, monometallic balance adjusted to temperature and five positions, shock absorber, and self-compensating Breguet hairspring. Its matching descriptions for Cal. 1030 and 1065 support a shared base with GMT work added.


Two details resist tidying. The Cal. 1030 descriptions name an index regulator; the 1066 descriptions stop short of the regulator, and at least one 6542 is catalogued with a free-sprung Glucydur balance instead. Whether that marks a running change or one cataloguer's shorthand is unresolved. The "butterfly" rotor, by contrast, is attested for the 1066 directly, on the circa-1959 example Phillips sold as lot 222 of The Geneva Watch Auction: XX.
The regulator and balance specification remain uncertain. Cal. 1030 descriptions name an index regulator, while Cal. 1066 descriptions omit it; one 6542 is catalogued with a free-sprung Glucydur balance. This may mark a running change or inconsistent cataloguing. A circa-1959 Phillips example directly confirms the Cal. 1066's butterfly rotor.


Documented 1066 examples cluster in 1958 and 1959: a steel 6542 stamped IV.1958 inside the caseback, an 18k yellow gold 1959 watch Antiquorum catalogued with a radium bakelite bezel and an orange-patinated dial, and the gold "Left-Hander" Phillips sold as lot 192 of The Geneva Watch Auction: EIGHT, which the house recorded as the first gold left-handed 6542 to reach the market. Rolex changed the caliber number with each running revision rather than keeping one number through the reference's life, which is why an early and a late 6542 can carry different movements despite looking identical from the dial side.
Documented examples cluster in 1958 and 1959, including a steel 6542 with a IV.1958 caseback and two gold watches dated to 1959. Rolex changed caliber numbers during the reference's run, so two outwardly similar 6542s can carry different movements.


<span id="cal-3075"></span>
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Cal. 3075 carries the synchronized "caller" GMT layout into the 16750 generation, and three houses describe it consistently. Antiquorum, New York, 15 December 2015, on a 16750: "Cal. 3075, 27 jewels, straight line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock absorber, self-compensating free-sprung Breguet balance spring, Microstella regulating screws, hack mechanism." Heritage catalogues a circa-1980 16750 as "Rolex Cal. 3075, rhodium finish, 27 jewels, automatic, monometallic balance adjusted to five positions and temperature," and a 1984 steel-and-gold 16753 as "Rolex caliber 3075, automatic, 27 jewels, adjusted five positions and temperature, monometallic balance, shock absorber." Twenty-seven jewels, straight-line lever, free-sprung Breguet on Microstella screws, hacking and quickset: all of that is on the record more than once. The quickset is worth stating precisely, though — Grail Watch Reference notes it only advances the date wheel.
Cal. 3075 carried the synchronized "caller" GMT layout into the 16750 generation. It has 27 jewels, a straight-line lever escapement, a monometallic balance adjusted to temperature and five positions, a free-sprung Breguet hairspring regulated by Microstella screws, hacking, and quickset. The quickset advances only the date wheel.


Two details in wide circulation do not survive those descriptions. The balance is monometallic, not Glucydur — Glucydur belongs to the 3135 generation that followed. And the regulating hardware is screws, with no house recording a count, a metal or a rim position; the "four gold Microstella screws on the inner rim" phrasing traces to text written about the later 3100 family and describes nothing any catalogue says about this caliber. Antiquorum's Geneva sale of 15 October 2006, lot 257, a gold 16758 made in 1983, gets no more specific than "free-sprung mono-metallic balance adjusted to temperatures and five positions, self-compensating Breguet balance spring, Microstella regulating screws." Shock protection is the same kind of gap: the houses record "shock absorber" and stop, so KIF here is an inference from Rolex's practice across the period rather than a documented specification.
The balance is monometallic, not Glucydur. Catalogue descriptions identify Microstella screws but do not record their count, material, or position on the rim. They also name a shock absorber without identifying its maker, so the KIF attribution remains inferred from Rolex practice of the period.


The 3075 belongs to the 3035 generation and shares its cantilevered balance cock, where the 3135 platform anchors the balance at both ends. Fratello's GMT-Master history marks that change one step later in this same branch: with the 3175 and 3185, "the construction of these movements changed and now featured a double balance-wheel bridge." Production dates need a correction. The caliber was never fitted to anything but the GMT-Master, and Grail Watch Reference notes that the 16750 "was not listed in the Rolex catalog until 1981," which leaves the widely repeated 1979 start with no host watch to sit in — though Antiquorum's own note on a 16758 lot dates that reference's production from 1979, so the disagreement runs through the auction record too. Fitments are the steel 16750, the steel-and-gold 16753 and the gold 16758. One small change here has outlasted everything else about the caliber: the 1575 stacked its GMT hand below the hour hand, the 3075 reversed the order, and every GMT caliber since has kept the 3075's arrangement.
The 3075 belongs to the 3035 generation and uses its cantilevered balance cock. Cal. 3175 and 3185 later introduced a balance bridge anchored at both ends. Its start date is disputed: the 16750 did not appear in a Rolex catalogue until 1981, while Antiquorum dates production of the 16758 to 1979. Known fitments are the steel 16750, steel-and-gold 16753, and gold 16758. The 3075 also moved the GMT hand above the hour hand, reversing the Cal. 1575 stack; later GMT calibers retained that arrangement.


<span id="cal-3085"></span>
<span id="cal-3085"></span>
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1983–89, 27 jewels, 28,800 vph, 48 hours, hacking, chronometer, built on the Cal. 3035 platform. The first Rolex caliber to dissociate the local-hour hand from the 24-hour hand: with the crown in its second position, turning it jumps the local hour hand forward or backward in full one-hour steps, snapping cleanly to each hour, while the minute and seconds hands and the 24-hour home-time hand stay undisturbed. A traveler resets local time without touching the hand that tracks home. Revolution's history of the line calls that independently settable hand the most important of the innovations the 1983 GMT-Master II brought to the collection. The cost is the quickset date, which from here advances only by running the local-hour hand around, a trade the caliber never bought back.
Cal. 3085 ran from 1983 to 1989 on the Cal. 3035 platform, with 27 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification. It was the first Rolex caliber to separate the local-hour hand from the 24-hour hand. The crown jumps the local hour forward or backward in one-hour steps without disturbing the minutes, seconds, or home-time hand. The date advances only by cycling the local-hour hand, so the movement has no direct quickset date.


Thickness is where the published record splits, and it matters because thickness is what gave the 16760 its "Fat Lady" and "Sophia Loren" nicknames. Grail Watch Reference gives 6.3mm, the figure that also runs through the general specification listings; Caliber Corner's specification sheet gives 7.2mm and sets it against the 6.45mm of the Cal. 3185 that replaced it. No Rolex document has surfaced that settles the figure, so both are recorded here rather than one being picked. The caliber ran in two references only — the 16760 GMT-Master II from 1983 and the 16550 Explorer II from 1985 — and the published specification listings agree on a Breguet hairspring, Microstella regulating screws and Kif shock protection. No auction description or Rolex document has been found that confirms the shock system directly, which is why the table entry above is flagged rather than stated flat.
Published thickness figures conflict. Grail Watch Reference gives 6.3mm, while Caliber Corner gives 7.2mm against the Cal. 3185's 6.45mm. This matters because the thicker movement and case produced the 16760's "Fat Lady" and "Sophia Loren" nicknames. Cal. 3085 appeared only in the 16760 GMT-Master II and 16550 Explorer II. Published specifications agree on a Breguet hairspring and Microstella regulation, but KIF shock protection has not been confirmed by an auction description or Rolex document.


<span id="cal-3130"></span>
<span id="cal-3175"></span>
=== Cal. 3130 ===
=== Cal. 3175 ===
[[File:Cal 3130 movement.webp|thumb|right|220px|Cal. 3130, engraved "3130," EmmyWatch]]
[[File:Cal 3175 movement.webp|thumb|right|220px|Cal. 3175, EmmyWatch]]
{| class="wikitable" style="width:280px; font-size:90%;"
{| class="wikitable" style="width:280px; font-size:90%;"
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| power reserve
| 48h
| 48h
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| size
| 28.5mm &times; 5.85mm
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| escapement
| escapement
Line 1,485: Line 1,492:
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|-
| balance
| balance
| Monometallic Glucydur, free-sprung
| Free-sprung Glucydur, Microstella
|-
|-
| regulator
| balance support
| Microstella screws, no index
| Balance bridge (3135 generation)
|-
|-
| shock
| shock
| KIF Elastor
| KIF Elastor (3100-family text, not lot-confirmed)
|}
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c.1999–2018, 31 jewels, 28,800 vph, 48 hours, hacking, chronometer — the time-only successor to Cal. 3000, carrying the 14060M, 114060, 114270, and 114200 through the 2000s and 2010s. The upgrade over the 3000 is a full balance bridge in place of a partial one, a larger balance wheel, and a Breguet overcoil hairspring. Calling it a date-less Cal. 3135 is not an analogy: Rolex's own parts sheet for the caliber prints "Base Calibre 3135" beneath a specification block reading Ø28.50mm, Ht 5.85mm, Train 28.800, 31 jewels. The start of the run is softer than the end — 1999, 2000 and 2001 all appear in print for the introduction, and no Rolex document has surfaced to settle it.
Cal. 3175 ran from 1988 to 1999 with 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, and chronometer certification. Auction descriptions confirm the jewel count and adjustment to temperature and five positions. The free-sprung Glucydur balance, Microstella regulation, Breguet hairspring, and KIF Elastor setting come from published 3100-family specifications rather than a Cal. 3175 lot. KIF Elastor is therefore probable, not directly confirmed.


That bridge is the substantive change. Cal. 3000 hung its balance from a cock anchored on one side only; the 3130 spans the balance with a bridge screwed down at both ends, which holds endshake stable under lateral shock and makes the larger, heavier balance wheel worth fitting in the first place. Antiquorum prints the rest of the regulating organ in full on the lots it has handled: rhodium-plated, straight-line lever escapement, monometallic balance adjusted to temperatures and five positions, shock absorber, self-compensating free-sprung Breguet balance spring, Microstella regulating screws, hack mechanism, in the wording used for a PVD-coated 14060M in New York on 10 March 2010, lot 164. Free-sprung is the load-bearing word. There is no regulator index on this movement; rate is set by turning the Microstella nuts on the Glucydur balance rim to move mass inward or outward and change the wheel's inertia. That is slower work on the bench than sliding an index, and it is why a 3130 holds its rate through a knock that would push a regulated movement out of tolerance. Shock protection is KIF Elastor rather than Rolex's own Paraflex, the single component that separates a 3130 from the Cal. 3132 that replaced it and the fastest way to place an open movement in the right decade. The height is worth getting right, because secondary listings routinely hand the 3130 the 3135's 6.00mm on the reasoning that the two are otherwise identical. Rolex's sheet has it 0.15mm thinner at 5.85mm, and that 0.15mm is the date mechanism the 3130 does without. The main plate is its own casting too, part 3130-100 rather than a reused 3135 item, though small pieces such as the screw for the dial distance piece still carry 3135 numbers.
Architecturally, Cal. 3175 is a Cal. 3135 with a fixed 24-hour hand. It uses the 3135's balance bridge, anchored at both ends, where Cal. 3075 used a cantilevered cock. The 24-hour hand remains linked to the local hour hand, so a second time zone is read from the rotating bezel. The 16700 kept this synchronized layout while the rest of the line moved to the jumping-hour Cal. 3185.


The caliber's odd distinction is that it spent its first years uncertified. The 14060M carried it from launch under a two-line dial with no chronometer designation, Rolex having declined to send the no-date Submariner's movements through COSC while certifying the same architecture in the Submariner Date alongside it. Certification came in late 2007 and the dial gained two more lines reading Superlative Chronometer Officially Certified. Nothing inside changed. The market has since inverted the logic and pays a premium for the two-liner, which makes the 3130 one of the few Rolex movements whose paperwork is worth less than its absence.
Cal. 3175 appeared only in the 16700 and was Rolex's last fixed GMT movement. Reports of factory Cal. 3185 fitment in late 16700s rest on a contradictory parts listing and a rebuilt watch; documented Cal. 3185 fitment belongs to the 16710. Sotheby's has incorrectly described Cal. 3175 as having an independent GMT hand. The accepted 16700 production span is 1988&ndash;1999, although Fratello gives 2001 in one account. The 1997 change from tritium to Super-LumiNova affected the dial, not the movement.


The known wear point sits in the automatic work rather than the escapement. The 3130 shares its oscillating-weight axle, Rolex part 568, with the 3135, 3155, 3175 and 3185, and that axle runs in a plain sleeve bearing rather than a ball race — fine while the oil holds, steadily worn once it migrates. A rotor that has developed play works a fine reddish dust through the movement, and replacing and riveting the axle is a routine bench job at service rather than a fault report. Sotheby's has sold the caliber in an Explorer 114270 of circa 2002 under the shortest description the house uses, cal. 3130 automatic, 31 jewels, which is roughly how the market treats it: a movement nobody argues about.
<span id="cal-3185"></span>
 
=== Cal. 3185 ===
One derivative is worth knowing about. Cal. 3131, announced in 2007, is the 3130 rebuilt for magnetic resistance: blue Parachrom hairspring, a paramagnetic escape wheel in nickel-phosphorus alloy, and a two-part soft-iron shield closed around the movement inside the case. It went into the Milgauss 116400 and 116400GV and later the Air-King 116900, which makes the 3130 the base of two quite different watches — an unremarkable no-date Submariner movement on one hand, and Rolex's answer to a thousand-gauss field on the other.
[[File:Cal 3185 movement.webp|thumb|right|220px|Cal. 3185, engraved "3185"]]
 
<span id="cal-3132"></span>
=== Cal. 3132 ===
[[File:Cal 3132 movement.webp|thumb|right|220px|Cal. 3132]]
{| class="wikitable" style="width:280px; font-size:90%;"
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| size
| size
| 30.97mm (contested; 28.5mm also published)
| 6.45mm
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Monometallic Glucydur, free-sprung
| Free-sprung Glucydur, four Microstella nuts
|-
| regulator
| Microstella screws, no index
|-
| shock
| Paraflex
|}
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2010–c.2020, 31 jewels, 28,800 vph, 48 hours, hacking, chronometer — Cal. 3130 with a Parachrom hairspring and Paraflex shock system added, powering the 214270 Explorer.
Cal. 3185 ran from 1989 to about 2007. Derived from Cal. 3135 with added 24-hour work, it has 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, chronometer certification, and KIF Elastor shock protection. It powered the 16710, 16713, 16718, and 16570, replacing Cal. 3085 in the GMT-Master II and Explorer II.


The base architecture is untouched: straight-line lever escapement, free-sprung monometallic Glucydur balance under a full bridge, Microstella regulating screws, no index. Bonhams catalogues it in the compressed form the house prefers — 31-jewel Cal. 3132 automatic, adjusted to temperature and 5 positions — for a DLC-coated 214270 carrying a cloisonné enamel world-map dial, sold at New Bond Street on 15 December 2021 as lot 54. What changed sits at either end of the balance staff. Paraflex replaced the KIF Elastor settings the 3130 used; Rolex's published figure for the gain is up to fifty per cent better shock resistance, from a spring geometry modelled in three dimensions so the setting cannot deform or unseat on impact. Parachrom replaced the Nivarox-type hairspring, a niobium-zirconium alloy that is paramagnetic by composition and blue by a surface oxide treatment Rolex patented separately from the alloy itself.
The balance carries four Microstella nuts arranged as two opposing pairs of different sizes. Rolex's Microstella wrench instructions require equal adjustment of both nuts in a pair to preserve the balance-wheel poise. Adjusting one without its opposite puts the wheel out of poise.


The 3132 matters more for what it marks than for what it does. Parachrom had been in Rolex movements since Cal. 4130 arrived in the 2000 Daytona, but the 214270 is where both Parachrom and Paraflex reach the time-only professional line, and the Submariner waited until Cal. 3230 in 2020 for either. For a decade the Explorer carried a technically newer regulating organ than the Submariner sitting beside it in the same catalogue, an inversion of the usual order that has quietly become one of the 214270's better arguments.
At 6.45mm, Cal. 3185 is slimmer than the Cal. 3085 it replaced, allowing the 16710 to sit flatter than the "Fat Lady" 16760. Its practical identification tell is visible during setting: the 24-hour hand twitches slightly as the local hour jumps. Cal. 3186 removed that play, so the test distinguishes the two without opening the case.


Both dial generations of the 214270 run the same caliber. The 2010 launch dial has short Mercedes hands and solid white-gold 3, 6 and 9 numerals with the luminous filling left out; the 2016 revision lengthens the hands and fills the numerals. Neither change reaches the movement, so the price gap between the two dials is entirely a dial argument. The 3132 also inherits the 3130's automatic work, including the plain-bearing oscillating-weight axle that wears once its lubricant migrates.
<span id="cal-3186"></span>
 
=== Cal. 3186 ===
The caliber's run also straddles a change in what its certification meant. Rolex redefined Superlative Chronometer in 2015, moving the guaranteed figure from COSC's &minus;4/+6 seconds a day on the bare movement to &minus;2/+2 on the cased watch, tested a second time in Rolex's own laboratories and backed by the green seal and a five-year international guarantee. A 214270 delivered in 2012 and one delivered in 2018 carry identical movements under different promises, which matters when a seller quotes a rate figure from the wrong side of that line.
[[File:Cal 3186 movement.webp|thumb|right|220px|Cal. 3186, engraved "3186"]]
 
<span id="cal-3175"></span>
=== Cal. 3175 ===
[[File:Cal 3175 movement.webp|thumb|right|220px|Cal. 3175, EmmyWatch]]
{| class="wikitable" style="width:280px; font-size:90%;"
{| class="wikitable" style="width:280px; font-size:90%;"
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| power reserve
| power reserve
| 48h
| 50h
|-
| size
| 28.5mm &times; 6.45mm
|-
|-
| escapement
| escapement
Line 1,572: Line 1,565:
|-
|-
| balance
| balance
| Free-sprung Glucydur, Microstella
| Monometallic, free-sprung
|-
|-
| balance support
| regulator
| Balance bridge (3135 generation)
| Microstella screws, no index
|-
|-
| shock
| shock
| KIF Elastor (3100-family text, not lot-confirmed)
| Shock-absorber, pre-Paraflex
|}
|}


1988–99, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer. The auction record is terser than Antiquorum's vintage paragraphs but consistent: Sotheby's catalogued a circa-1996 example in its Watches Online sale of 2020 as "cal. 3175 automatic, 31 jewels," movement no. 7'693'716; Christie's catalogued a circa-1992 16700 in December 2021 as "cal. 3175 automatique, 31 rubis"; and a circa-1997 example is described as "31-jewel Cal.3175 automatic, adjusted to 5 positions & temperatures," movement no. 38001877 — the five-positions-and-temperature wording being the standard chronometer adjustment statement of the period. The Glucydur balance, free-sprung on Microstella, the Breguet hairspring and the KIF Elastor shock setting come from Grail Watch Reference's entry on the 3100 family rather than from any lot, none of which itemises them — and that entry hedges its own shock claim, saying most 3100 movements use the Kif Elastor setting rather than all of them.
Cal. 3186 ran from 2007 to 2019. It added a Parachrom hairspring to the Cal. 3185 base while retaining 31 jewels, a 28,800 vph frequency, hacking, quickset, and chronometer certification; reserve increased to 50 hours. It powered late 16710 production and the ceramic-bezel 116710LN, 116710BLNR, and 116719BLRO.


Architecturally this is Cal. 3135 with a fixed 24-hour hand, and it takes that platform's balance bridge with it, anchored at both ends where the 3075 before it used a cantilevered cock. Fratello's GMT-Master history dates the arrival of the "double balance-wheel bridge" to this caliber and the 3185 introduced alongside it. The 24-hour hand stays linked to the local hour hand, so the second time zone reads off the rotating bezel rather than an independent hand — the older synchronized layout, kept alive on a single reference right to the end of the 1990s while the rest of the line had moved to the jumping-hour Cal. 3185.
The movement has a straight-line lever escapement, monometallic balance adjusted to temperature and five positions, shock protection, a free-sprung Breguet-form hairspring, Microstella regulation, and hacking. One Antiquorum description calls the hairspring blued steel, but Cal. 3186 uses Parachrom, a niobium-zirconium alloy coloured by an oxide layer rather than tempering.


It ran in the 16700 and nowhere else, and it closes a line. Hodinkee's Reference Points survey calls it "Rolex's last 'fixed' GMT movement, with all subsequent calibers allowing for independent operation of the GMT and hour hands," which holds up against the one caliber that could break it: Cal. 3187, filed under the plain GMT heading rather than GMT-Master II, has an independently adjustable 24-hour hand. Reports that late 16700s left the factory with a Cal. 3185 do not stand — the examples circulating trace to a self-contradictory parts listing and a rebuilt watch, and the 3185's reference is the 16710. The caliber's defining trait is misreported at house level too: Sotheby's own collector's guide to the line credits the 16700's Cal. 3175 with "the independent flying GMT hand," which is the one thing it does not have. The 16700's own span carries a minor disagreement worth keeping: 1988 to 1999 is the standard figure, and Fratello has put the end at 1999 in one passage and 2001 in another. Monochrome's account notes that almost nothing changed across the run beyond tritium giving way to Super-LumiNova in 1997 — a dial change, with the caliber untouched.
Cal. 3186 retains the Cal. 3135 architecture used by the 3185: 28.5mm diameter, 6.45mm height, 28,800 vph, and 31 jewels. It also keeps the plain-bearing oscillating-weight axle, part 568, shared with Cal. 3130, 3135, 3155, and 3175. Once lubricant migrates, the axle wears and requires replacement and riveting at service.


<span id="cal-3185"></span>
Rolex introduced Cal. 3186 as a running change, leaving its start date unsettled. Steel 16710 examples begin among late Z- and M-series cases; the lowest documented example is Z 5786xx, but higher Z-series watches can still contain Cal. 3185. Gold references changed earlier. A D-series 116718 catalogued with Cal. 3186 was sold in August 2006, placing the movement in production before the commonly cited 2007 steel transition.
=== Cal. 3185 ===
 
[[File:Cal 3185 movement.webp|thumb|right|220px|Cal. 3185, engraved "3185"]]
Both Cal. 3185 and 3186 index the local-hour hand with a jumping-hour click. Cal. 3186 reworked the parts and reduced slack between the drive-train wheels. As a result, the 24-hour hand twitches when the local hour jumps on a 3185 but remains still on a 3186. This identifies the caliber without removing the caseback.
 
The jumping-hour click spring is the caliber's known failure point. A failed spring lets the local-hour hand glide instead of indexing in one-hour steps and can leave it loose on its wheel. Rolex superseded part 657 first with 657-1 and then 657-2; the later springs are stronger and slightly larger. The fault is documented across the 16710, 16570, 116710, 116713, 116718, and 116719, as well as Cal. 3187. It does not normally damage other components, but the hour-jump action should be checked on an unserviced watch.
 
<span id="cal-3187"></span>
=== Cal. 3187 ===
[[File:Cal 3187 movement.webp|thumb|right|220px|Cal. 3187, official Rolex photo, engraved "3187," blue Parachrom hairspring, free-sprung Microstella balance]]
{| class="wikitable" style="width:280px; font-size:90%;"
{| class="wikitable" style="width:280px; font-size:90%;"
! detail
! detail
Line 1,604: Line 1,603:
|-
|-
| power reserve
| power reserve
| 48h
| 48–50h (sources disagree)
|-
|-
| size
| size
| 6.45mm
| 30.97mm (contested; 28.5mm also published)
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Free-sprung Glucydur, four Microstella nuts
| Monometallic, free-sprung
|-
| regulator
| Microstella screws, no index
|-
| shock
| Paraflex
|}
|}


1989–c.2007, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer, KIF Elastor shock. Derived from the Cal. 3135 platform with a 24-hour hand mechanism added, powering the 16710, 16713, 16718, and 16570. Published reference listings date its service in the Explorer II 16570 to 1989–2006 and in the GMT-Master II 16710 to 1989–2005; Grail Watch Reference records the same 1989 introduction, replacing the short-lived Cal. 3085 in both models.
Cal. 3187 is an enlarged Cal. 3186, widened to move the date window outward in the 42mm Explorer II case. It powered only the 216570 from 2011 to 2021, before Cal. 3285 replaced it in the 226570. The Parachrom hairspring, Breguet overcoil, and independently adjustable local-hour hand carry over from the GMT lineage. Paraflex is new here, replacing the KIF Elastor used by Cal. 3185 and making Cal. 3187 the first movement in this family with Rolex's own shock system.
 
Cal. 3187 uses a larger baseplate and reworked surrounding parts but retains the Cal. 3186 regulating organ: a straight-line lever escapement, free-sprung monometallic balance under a full bridge, and Microstella regulation without an index. Auction catalogues confirm 31 jewels but do not itemize those inherited components.
 
Rolex launched the 216570 and Cal. 3187 together in March 2011 for the Explorer II's fortieth anniversary. The 42mm case required the larger movement, while the orange 24-hour hand recalled the 1655. Both remained in production until 2021, and no other reference used the caliber.
 
Two documented unit commissions use Cal. 3187. A 2012 white-dial 216570 made for members of the British Special Air Service carries "Who Dares Wins," the winged-dagger badge, and its owner's identifiers. A circa-2015 example numbered 40/48 was made for the UK Attack Helicopter Force. These were unit commissions rather than ministry-issued watches and should not be classified with the 5513 MilSub.


The balance carries four Microstella nuts, and the point is worth making because the two-nut reading circulates widely. Grail Watch Reference describes Microstella regulation by four screws set inside the balance rim, Monochrome's account of the Rolex regulator describes the free-sprung balance as carrying two pairs of Microstella nuts, and the hands-on regulation writeup of a 3185-powered GMT-Master II at Minus4Plus6 photographs four, arranged as two opposing pairs of different sizes. What gets adjusted in pairs is the pair, not the balance as a whole: the instruction sheet supplied with Rolex's own Microstella wrench states that the adjustment of a pair of nuts, short or long, must be identical so as not to modify the balance-wheel poising, and Caliber Corner repeats the warning in the same terms. Turn one nut of a pair without its opposite and the wheel goes out of poise.
Cal. 3187 inherited the 3186's jumping-hour click-spring failure. On affected watches, the local-hour hand glides instead of indexing in one-hour steps. Rolex revised the part twice, and serviced examples may carry the later, stronger spring.


At 6.45mm on Caliber Corner's figures the movement is slimmer than the Cal. 3085 it replaced, part of why the 16710 wears flatter than the "Fat Lady" 16760. The everyday tell between this caliber and the later 3186 shows up in the hands rather than in any engraving: on the 3185, setting the time drags the 24-hour hand slightly along with it, a coupling the 3186 removed, and that drag is the quick way to identify which of the two a GMT is running without opening the case.
The &minus;2/+2 rating applies only after Rolex redefined Superlative Chronometer in 2015. Earlier watches carried the COSC &minus;4/+6 seconds-per-day standard for the uncased movement; later examples were tested again by Rolex as complete watches. The underlying caliber did not change beyond regulation.


<span id="cal-3186"></span>
<span id="sport-modern"></span>
=== Cal. 3186 ===
== Modern sport calibers (1988–2020) ==
[[File:Cal 3186 movement.webp|thumb|right|220px|Cal. 3186, engraved "3186"]]
 
{| class="wikitable" style="width:280px; font-size:90%;"
The modern time-only line begins with Cal. 3000, the first 28,800 vph no-date movement of the period, followed by Cal. 3130 and 3132. The date-equipped Cal. 3135 reached the Submariner two years earlier and remained Rolex's main date movement through three decades of Submariner Date production.
 
<span id="cal-3000"></span>
=== Cal. 3000 ===
[[File:Cal 3000 movement.webp|thumb|right|220px|Cal. 3000]]
{| class="wikitable" style="width:280px; font-size:90%;"
! detail
! detail
! value
! value
Line 1,630: Line 1,649:
|-
|-
| jewels
| jewels
| 31
| 27
|-
|-
| frequency
| frequency
Line 1,636: Line 1,655:
|-
|-
| power reserve
| power reserve
| 50h
| 42h (48h in some sources)
|-
|-
| size
| size
| 28.5mm &times; 6.45mm
| 28.5mm × 5.8mm
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Monometallic, free-sprung
| Adjustable-mass, flat hairspring
|-
| regulator
| Microstella screws, no index
|-
| shock
| Shock-absorber, pre-Paraflex
|}
|}


2007–19, 31 jewels, 28,800 vph, 50 hours, hacking, quickset, chronometer — adds a Parachrom hairspring to the Cal. 3185 base, carrying late 16710 production into the ceramic-bezel GMT line, the 116710LN, 116710BLNR, and 116719BLRO.
Cal. 3000 is the no-date member of the 3000 family, used from about 1990 to 2001 in the Air-King 14000 and 14010, Submariner 14060, and Explorer 14270. The often-quoted 1988 start belongs to Cal. 3135. The Air-King changed to reference 14000M in 2000, while the Explorer became the 114270 and the Submariner adopted Cal. 3130 in 2001. Published power-reserve figures conflict at 42 and 48 hours; no Rolex figure settles the difference.


Antiquorum's cataloguing is the fullest description of the movement in the public record: Cal. 3186, rhodium-plated, oeil de perdrix and fausses côtes decoration, 31 jewels, straight-line lever escapement, monometallic balance adjusted to temperatures and five positions, shock-absorber, self-compensating free-sprung Breguet balance spring, Microstella regulating screws, hack mechanism, from sale 214 in Geneva on 10 May 2009, lot 38. Bonhams describes the same caliber in a second 116718 with its own house wording — 31-jewel Cal. 3186, straight line lever escapement, monometallic balance, adjusted to heat, cold, isochronism and 5 positions, shock protection, self compensating balance spring — and the two agree on every mechanical point. One phrase in the Antiquorum text is boilerplate rather than observation: the balance spring is called blued steel, and on a 3186 it is Parachrom, a niobium-zirconium alloy whose colour comes from an oxide layer rather than from tempering. That spring is the caliber's reason for existing.
Cal. 3000 was Rolex's last movement without a Breguet overcoil. It uses a flat hairspring, unlike the outgoing 1570 generation and the rest of the 3000 family. Rate is set by Microstella adjustment rather than an index, the hairspring is glued to the balance stud, and shock protection is KIF. COSC certification used the standard &minus;4/+6 seconds-per-day tolerance.


Underneath the GMT work the movement is Cal. 3135 architecture, and Rolex states it outright: the factory parts sheet for the 3185 heads its specification block with Ø28.50mm, Ht 6.45mm, Train 28.800, 31 jewels and the line "Base Calibre 3135." The 3186 keeps that layout. That inheritance runs to the automatic work as well, including the oscillating-weight axle, Rolex part 568, shared with the 3130, 3135, 3155 and 3175 — the plain-bearing rotor post that wears once its oil has migrated and gets replaced and riveted at service.
<span id="cal-3035"></span>
 
=== Cal. 3035 ===
Rolex introduced the 3186 as a running change rather than an announcement, which is why its start date is unsettled. The 2007 date reflects the steel transition collectors actually track, when late Z- and M-serial 16710s began leaving Geneva with the new caliber; the lowest documented 16710 example is a Z 5786xx, but the changeover was not sequential and Z-serials well above that number have turned up with 3185s inside. The gold references ran ahead of the steel. The Antiquorum lot above is a 116718 on a D-series case sold in August 2006 and catalogued as a 3186, which puts the movement in series production at least a year before the transition most owners date it to.
[[File:Cal 3035 movement.webp|thumb|right|220px|Cal. 3035, engraved "3035," EmmyWatch]]
 
{| class="wikitable" style="width:280px; font-size:90%;"
The break from the 3185 is not only the hairspring, and it is narrower than the usual telling. Both calibers index the local-hour hand with a jumping-hour click: Rolex's parts sheet for the 3185 lists the click at 5242 and its spring at 5243, next to a friction spring for the additional hour wheel at 5226. What the 3186 does is rework that arrangement onto its own part series and pull the drive-train wheels closer together, taking the slack out of the independently-set hand. That produces the field diagnostic the market runs on. Jump the hour hand on a 3185 and the 24-hour hand twitches visibly as the play takes up; on a 3186 it stays put. No caseback needs to come off.
 
The click spring is also the caliber's known failure. When it goes, the hour hand stops indexing in clean one-hour steps and glides freely instead, which makes local-time setting useless and in the worst cases leaves the hand loose on its wheel. Rolex's own parts numbering records the response: the jumping-hour click begins as part 657, is superseded by 657-1, and then by 657-2, the later springs stronger and slightly larger than the first. Owners on RolexForums have documented the failure across the 16710, 16570, 116710, 116713, 116718 and 116719 and on into the Cal. 3187 that followed, with service centres replacing the spring at no charge on some watches long out of warranty and charging for it inside a full service on others. It is a spring rather than a catastrophe — nothing else is damaged when it breaks — but on a caliber produced in these numbers it is the first thing worth checking on an unserviced 3186 GMT.
 
<span id="cal-3187"></span>
=== Cal. 3187 ===
[[File:Cal 3187 movement.webp|thumb|right|220px|Cal. 3187, official Rolex photo, engraved "3187," blue Parachrom hairspring, free-sprung Microstella balance]]
{| class="wikitable" style="width:280px; font-size:90%;"
! detail
! detail
! value
! value
Line 1,677: Line 1,679:
|-
|-
| jewels
| jewels
| 31
| 27
|-
|-
| frequency
| frequency
Line 1,683: Line 1,685:
|-
|-
| power reserve
| power reserve
| 48–50h (sources disagree)
| 48h
|-
| size
| 30.97mm (contested; 28.5mm also published)
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Monometallic, free-sprung
| Free-sprung, four Microstella screws
|-
| regulator
| Microstella screws, no index
|-
|-
| shock
| shock
| Paraflex
| KIF Elastor
|}
|}


An enlarged Cal. 3186, widened to push the date window outward for the 42mm Explorer II case — the same engineering trick Rolex used two years earlier on Cal. 3136 for the Datejust II. It powers the Explorer II 216570 exclusively, the first movement developed specifically for the Explorer line, running 2011 to 2021 before the 226570 and Cal. 3285 replaced it. Parachrom hairspring and Breguet overcoil carry over from the 3185/3186 GMT lineage, paired with an independently-adjustable 24-hour GMT hand and a Superlative Chronometer &minus;2/+2 rating. Paraflex does not carry over: the 3185 ran KIF Elastor settings and the 3187 is the first movement in this GMT family fitted with Rolex's own shock system.
Cal. 3035 ran from 1977 to 1988 in the 16800, 168000, 16808, and 16803. It was the first quickset Submariner caliber, with 27 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification. Compared with the Cal. 1570 generation, it increased frequency from 19,800 vph and added a crown position that advances the date wheel directly. Its free-sprung Nivarox Breguet overcoil is regulated by four Microstella screws and protected by KIF Elastor.


Auction descriptions of the 3187 are thin next to the 3186's. Sotheby's catalogues it as cal. 3187 automatic, 31 jewels and stops, so the mechanical detail comes from the relationship rather than from lot text. The 3187 is a 3186 on a larger baseplate with the surrounding parts reworked, which carries the straight-line lever escapement, the free-sprung monometallic balance under a full bridge, and the Microstella screws that set rate by inertia rather than by an index. Nothing in the regulating organ was redesigned; the movement grew to reach the date window at a wider radius, and everything that governs its rate came across unchanged.
Two construction details separate it from Cal. 3135. Its balance sits on a cantilevered cock rather than a bridge anchored at both ends, and its hairspring is glued to the stud rather than laser-welded.


Reference and caliber share a lifespan exactly. Rolex launched both at Basel in March 2011 for the Explorer II's fortieth anniversary, pulling the orange 24-hour hand back from the 1655 after two generations of red and white, and stretching the case to 42mm — which is what forced the movement to grow in the first place. The 216570 ran a full decade to 2021, and no other reference ever received the 3187, which leaves it among the very few modern Rolex calibers with a single home.
<span id="cal-3130"></span>
 
=== Cal. 3130 ===
Two documented military commissions sit on top of the ordinary run. Sotheby's sold a white-dial 216570, movement number 9C'034'251, from a 2012 series issued to members of the British Special Air Service, its case band engraved "Who Dares Wins" and its caseback carrying the winged-dagger badge above the original owner's initials and personal number, as lot 11 of Fine Watches Including Masterworks of Time. Bonhams sold a second commission, a 216570 numbered 40/48 from a limited series made for the UK Attack Helicopter Force, circa 2015. Both are unit-commissioned rather than ministry-issued, which puts them in a different class from a 5513 MilSub, and both are the only regiment-marked Explorer IIs in the auction record. Both run the 3187.
[[File:Cal 3130 movement.webp|thumb|right|220px|Cal. 3130, engraved "3130," EmmyWatch]]
 
{| class="wikitable" style="width:280px; font-size:90%;"
The 3187 inherited the 3186's weak point along with its architecture. The jumping-hour click spring that lets the local-hour hand index in whole-hour steps fails the same way on early examples, the hand gliding instead of clicking, and owners have reported it on the 216570 as readily as on the ceramic GMTs. Rolex revised the part twice; a serviced example carries the later, stronger spring.
! detail
 
! value
The &minus;2/+2 figure needs a date attached to it. Rolex redefined Superlative Chronometer in 2015, taking the guaranteed rate from COSC's &minus;4/+6 seconds a day on the bare movement to &minus;2/+2 on the cased watch, tested again in Rolex's own laboratories and sold under a green seal with a five-year international guarantee. The 216570 ran on both sides of that change. A 2012 example left Geneva under the older promise and a 2018 example under the newer one, with no mechanical difference between the two beyond regulation, so the tighter number belongs to the second half of the reference's life rather than to the caliber as such.
 
<span id="sport-modern"></span>
== Modern sport calibers (1988–2020) ==
 
The modern time-only line settles on the 31xx family, opening with Cal. 3000 as the first 28,800 vph no-date movement of the era and running through Cal. 3130 and 3132 in direct succession. Cal. 3135, the date-equipped caliber that reached the Submariner two years ahead of it, becomes the single dominant modern Rolex workhorse across three decades of Submariner Date production.
 
<span id="cal-3000"></span>
=== Cal. 3000 ===
[[File:Cal 3000 movement.webp|thumb|right|220px|Cal. 3000]]
{| class="wikitable" style="width:280px; font-size:90%;"
! detail
! value
|-
|-
| type
| type
Line 1,729: Line 1,709:
|-
|-
| jewels
| jewels
| 27
| 31
|-
|-
| frequency
| frequency
Line 1,735: Line 1,715:
|-
|-
| power reserve
| power reserve
| 42h (48h in some sources)
| 48h
|-
|-
| size
| size
| 28.5mm × 5.8mm
| 28.5mm &times; 5.85mm
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Adjustable-mass, flat hairspring
| Monometallic Glucydur, free-sprung
|-
| regulator
| Microstella screws, no index
|-
| shock
| KIF Elastor
|}
|}


Roughly 1990 to 2001, 27 jewels, 28,800 vph, 28.5 × 5.8mm — the date-less member of the 3000 family, behind the 14000 Air-King, the 14010, the 14060 Submariner and the 14270 Explorer. The 1988 start date sometimes quoted belongs to Cal. 3135; Grail Watch Reference and Caliber Corner both put the 3000's introduction at 1990, and Grail Watch tracks the handover to Cal. 3130 reference by reference — the Air-King becoming the 14000M in 2000, the Explorer the 114270 in 2001, with the 14060 Submariner carrying the 3000 from 1990 through 2001. Power reserve is unsettled. Caliber Corner's spec sheet gives 42 hours, Fratello's 14270 write-up gives 48, and no Rolex figure has surfaced to decide between them.
Cal. 3130 is the time-only successor to Cal. 3000, used in the 14060M, 114060, 114270, and 114200. It brought a full balance bridge, a larger balance wheel, and a Breguet overcoil hairspring. Rolex's parts sheet identifies Cal. 3135 as the base and gives 28.5mm diameter, 5.85mm height, 28,800 vph, and 31 jewels. Published introduction dates range from 1999 to 2001; the precise year remains unsettled.
 
Cal. 3000 supports its balance from a cock anchored on one side; the 3130 uses a bridge secured at both ends, which stabilizes endshake under lateral shock. Its Glucydur balance is free-sprung, with rate set by Microstella nuts rather than an index. KIF Elastor shock protection distinguishes it from the Paraflex-equipped Cal. 3132. At 5.85mm it is 0.15mm thinner than Cal. 3135 because it omits the date mechanism. The main plate is the dedicated part 3130-100, although some smaller components retain 3135 part numbers.
 
The 14060M initially used Cal. 3130 without COSC certification and carried a two-line dial. Certification arrived in late 2007, adding the two-line "Superlative Chronometer Officially Certified" inscription. The movement itself did not change.
 
The main wear point is the oscillating-weight axle, Rolex part 568, shared with Cal. 3135, 3155, 3175, and 3185. It runs in a plain sleeve bearing rather than a ball bearing. Once lubricant migrates, axle wear can produce rotor play and fine reddish dust. Replacing and riveting the axle is a routine service repair.


The regulating organ is what makes the caliber unusual, and it runs against the direction of travel. Grail Watch Reference calls Cal. 3000 the last Rolex movement built without a Breguet overcoil — a flat hairspring, where the outgoing 1570 generation and every other member of the 3000 family carry an overcoil — and Caliber Corner's spec sheet records the hairspring the same way. Rate is still set by inertia rather than by an index: Grail Watch Reference has the whole family on Microstella regulation with the hairspring glued to the balance stud, and Caliber Corner lists KIF shock protection. Certification went through COSC at the standard −4/+6 seconds per day, which Fratello notes on the 14270.
Cal. 3131, announced in 2007, adapts the 3130 for magnetic resistance with a blue Parachrom hairspring, a paramagnetic nickel-phosphorus escapement, and a two-part soft-iron shield around the movement. It powered the Milgauss 116400 and 116400GV, then the Air-King 116900.


<span id="cal-3035"></span>
<span id="cal-3132"></span>
=== Cal. 3035 ===
=== Cal. 3132 ===
[[File:Cal 3035 movement.webp|thumb|right|220px|Cal. 3035, engraved "3035," EmmyWatch]]
[[File:Cal 3132 movement.webp|thumb|right|220px|Cal. 3132]]
{| class="wikitable" style="width:280px; font-size:90%;"
{| class="wikitable" style="width:280px; font-size:90%;"
! detail
! detail
Line 1,759: Line 1,754:
|-
|-
| jewels
| jewels
| 27
| 31
|-
|-
| frequency
| frequency
Line 1,766: Line 1,761:
| power reserve
| power reserve
| 48h
| 48h
|-
| size
| 30.97mm (contested; 28.5mm also published)
|-
| escapement
| Swiss lever
|-
|-
| balance
| balance
| Free-sprung, four Microstella screws
| Monometallic Glucydur, free-sprung
|-
| regulator
| Microstella screws, no index
|-
|-
| shock
| shock
| KIF Elastor
| Paraflex
|}
|}


1977 to 1988, 27 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer — the first quickset Submariner caliber, in the 16800, 168000, 16808 and 16803. Grail Watch Reference sets the run at 1977 through 1988, describes the movement as developed alongside the Oysterquartz Cal. 5035, and gives the two headline changes over the 1570 generation it replaced: balance speed up from 19,800 to 28,800 vph, and a quickset that advances the date wheel alone. That is the whole trick of quickset — an intermediate crown position driving the date wheel directly, where a non-quickset caliber can only reach the date by running the hands forward through midnight. The regulating package is a free-sprung Breguet overcoil in Nivarox alloy on four Microstella screws, with KIF Elastor shock protection.
Cal. 3132 powered the Explorer 214270 from 2010 to about 2020. It is a Cal. 3130 with a Parachrom hairspring and Paraflex shock protection, retaining 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification.
 
The base architecture remains a straight-line lever escapement with a free-sprung Glucydur balance under a full bridge, Microstella regulation, and no index. Paraflex replaced the 3130's KIF Elastor settings; Rolex claimed up to 50 per cent greater shock resistance. The blue Parachrom hairspring replaced Nivarox with a paramagnetic niobium-zirconium alloy whose colour comes from a patented oxide treatment.
 
Cal. 3132 brought Parachrom and Paraflex to the time-only professional line. Parachrom had appeared in Cal. 4130 in 2000, but the Submariner did not receive both features until Cal. 3230 in 2020.


Two construction details separate it from the Cal. 3135 that replaced it, and both come up again in the 3135 entry below. The balance sits on a cantilevered cock anchored at one end, where the 3135 introduced a bridge screwed down at both ends. And the hairspring is glued to its stud rather than laser-welded, a trait Grail Watch Reference attributes to the entire 3000 family and not to this caliber alone.
Both dial generations of the 214270 use Cal. 3132. The 2016 revision lengthened the hands and added luminous filling to the 3, 6, and 9 numerals, without changing the movement. Cal. 3132 also retains the 3130's plain-bearing oscillating-weight axle, which wears after its lubricant migrates.
 
Rolex redefined Superlative Chronometer in 2015, changing the guaranteed rate from COSC's &minus;4/+6 seconds per day on the uncased movement to &minus;2/+2 on the cased watch after additional in-house testing. The movement did not change, so early and late 214270 examples carry different rate guarantees.


<span id="cal-3135"></span>
<span id="cal-3135"></span>
Line 1,813: Line 1,823:
|}
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1988–2021, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer — Rolex's thirty-year workhorse, running the 16610, 16613, and 16618 through to the 116610 generation and leaving the Submariner only when the 126610 arrived with Cal. 3235 on 1 September 2020. That was not quite the end of it. The Oyster Perpetual Date 34, references 115200 and 115234, kept the caliber in current production into 2021: rolex.com was still listing calibre 3135 on the 115200 specification page in February 2021, and the model family dropped off the site ahead of that April's catalogue refresh. Claims that the 3135 ran to 2022 or 2023 come from conflation with Cal. 3131, the Milgauss and Air-King derivative, which genuinely did. Rhodium-plated finish, beveled and polished chamfered screws, and a two-piece axle-style bidirectional rotor.
Cal. 3135 ran from 1988 to 2021 with 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, and chronometer certification. It powered the 16610, 16613, and 16618 through the 116610 generation. The Submariner changed to Cal. 3235 with the 126610 on 1 September 2020, but the Oyster Perpetual Date 34 references 115200 and 115234 kept Cal. 3135 in production into 2021. Later end dates conflate it with Cal. 3131. The movement has rhodium plating, bevelled and polished screws, and a two-piece axle-style bidirectional rotor.


The escapement is a conventional Swiss lever; the interest sits in the oscillator above it. The balance is Glucydur, the beryllium-bronze alloy Rolex had been using since the 1950s, and it runs free-sprung, with no index and no curb pins, so rate is set by turning four Microstella nuts and changing the wheel's inertia instead of the working length of the spring. Those nuts sit on the inside of the balance rim, a 3135-generation trait: the older 1530-family balances carry their equivalent adjustable screws on the outside, where a clockwise turn draws the screw inward and speeds the watch up. The hairspring terminates in a Breguet overcoil, and where Cal. 3035 glued its hairspring to the balance stud, the 3135 laser-welds it.
The conventional Swiss lever escapement is paired with a free-sprung Glucydur balance. With no index or curb pins, four Microstella nuts on the inside of the rim set the rate by changing the wheel's inertia. Older 1530-family balances place their adjustment screws on the outside. Cal. 3135 uses a Breguet overcoil and laser-welds the hairspring to its stud, replacing the glued joint used by Cal. 3035.


The architectural change from the 3035 is the balance bridge. The 3035 carried a cantilevered balance cock anchored at one end by a single screw; the 3135 replaced it with a bridge (part 3135-120) screwed down at both ends and carrying height-regulating nuts, which holds the pivots in alignment under load and makes endshake adjustable without shimming. Watchmakers who have had both apart describe the 3035's signature failures as broken automatic-weight axles and axle jewels plus a hairspring that fouls on the balance cock, the second of which the bridge answers directly. The 3135 also went from 27 jewels to 31 and took a larger balance wheel.
The main architectural change from Cal. 3035 is the balance bridge. Part 3135-120 is secured at both ends and carries height-adjusting nuts, keeping the pivots aligned under load and allowing endshake adjustment without shims. It also prevents the hairspring from fouling a cantilevered balance cock, a known Cal. 3035 problem. Cal. 3135 increased the jewel count from 27 to 31 and uses a larger balance wheel.


Shock protection is the detail most often reported wrongly. For its entire run the base 3135 used KIF, the hinged spring-mounted setting Rolex bought from Kif Parechoc for decades. Paraflex, Rolex's own shock absorber, filed from a March 2005 priority by Mitchell Colle and Roman Voirol and published as EP1705537 and US7234859, never went into it. Rolex handled the upgrade by renumbering instead: the base date caliber stayed 3135 with KIF, while the Paraflex version became Cal. 3136, the physically larger movement built for the Datejust II in 2009. The same pattern runs across the family, 3130 to 3132, 3155 to 3156, 3186 to 3187, so a Paraflex caliber always carries its own number. Listings that credit a 16610 or a 116610 with Paraflex are describing a movement Rolex did not build.
Cal. 3135 used KIF shock protection throughout its run and never received Paraflex. Rolex assigned new caliber numbers to Paraflex versions: 3130 became 3132, 3155 became 3156, and 3186 became 3187. The larger Paraflex date movement for the Datejust II was Cal. 3136. A 16610 or 116610 described as having Paraflex is therefore misidentified.


The hairspring is the running change that lets a collector date a movement without opening the case, though not as precisely as usually claimed. Parachrom is a niobium-zirconium alloy with traces of titanium, vanadium and tantalum, patented by Rolex from a March 1999 priority filing by Jacques Baur and Patrick Sol. Nb-Zr grows an uneven oxide film in air, which shifts the spring's restoring torque and with it the rate; the fix was to force a uniform anodised layer of roughly 50 nanometres, and that is what turns the spring blue. The colour is a by-product of that treatment: vary the anodising voltage and the colour varies with it, and early prototypes came out greenish. When it reached the 3135 is unsettled. Parachrom appeared first in the Daytona's Cal. 4130 around 2000 and the blue anodised version followed mid-decade; for the 3135 itself Grail Watch Reference dates the change to 2009, other accounts put it nearer 2005, and watchmakers report transitional late 14060M and 114060M examples either side of the line. The ceramic-bezel 116610 of 2010 carries it consistently. Any single year is a rough marker, not a hard cut.
Parachrom arrived during the Cal. 3135 run, but the transition date is unsettled. The niobium-zirconium alloy receives a uniform anodised oxide layer about 50 nanometres thick, which gives the hairspring its blue colour and stabilizes its restoring torque. Published dates for its adoption in Cal. 3135 range from about 2005 to 2009, with transitional examples reported on both sides. The ceramic-bezel 116610 uses it consistently from 2010. The spring's colour is therefore only a rough dating marker.


Two wear points define the caliber's service life, and both sit in the automatic works. The reversing wheels (Rolex part 3135-540, "reversing wheel, mounted") are anodised purple-red and visible straight through the rotor cutout, an easy no-disassembly identification marker; Rolex dates that red finish to 1957 and describes it as a surface treatment applied to aluminium for hardness. They are also the most commonly reported fault on the caliber, presenting as a rotor that spins freely without winding the mainspring, or as gritty manual winding. The correct treatment is epilame across the whole reverser assembly with oil confined to the arbor and bearing points, never the teeth or the clicks, since oil migrating between the teeth and the red disc eventually jams the mechanism. The second is the oscillating-weight axle (part 3135-568), which runs against a plain jewelled sleeve rather than a ball bearing and is the signature failure of a long-unserviced example: an audible rattle, the rotor striking the case back, and red wear-dust carried through the movement. Andrew Babanin's 2005 teardown and Ashton Tracy's 2018 write-up in the ''Horological Journal'' reach the same conclusion thirteen years apart. Rolex stocked the mainspring in two factory strengths, 3135-311 and the weaker 3135-311-1, which is worth knowing on a movement someone else has rebuilt.
Two wear points sit in the automatic works. The anodised purple-red reversing wheels, part 3135-540, are visible through the rotor cutout and identify the movement without disassembly. Failure produces free rotor spin without winding or gritty manual winding. Epilame belongs across the reverser assembly, while oil is confined to the arbor and bearing points; oil on the teeth or clicks can jam the mechanism. The oscillating-weight axle, part 3135-568, runs in a plain jewelled sleeve. Wear causes a rattle, rotor contact with the caseback, and red dust in the movement. Rolex supplied mainsprings in standard part 3135-311 and weaker 3135-311-1 versions, a relevant distinction when assessing a rebuilt movement.


For a health check, a freshly serviced 3135 should show roughly 270 to 310 degrees of amplitude fully wound; much above 335 suggests the mainspring is slipping its bridle too late for want of braking grease, and Rolex's own timing procedure sets the floor at 200 degrees after 24 hours in the worst position. On certification, every 3135 went to COSC as a bare movement against the -4/+6 seconds-per-day standard. In 2015 Rolex redefined its own Superlative Chronometer marking to -2/+2 seconds per day measured on the finished, cased watch and applied it across the catalogue, so the caliber's final years of production were held to the tighter in-house figure with the movement itself unchanged. The dial text is the tell, not the caliber. Derivatives run to the 3155 (day-date), 3175, 3185 and 3186 (GMT-Master II, the 3186 gaining an independently adjustable local-hour hand), 3187 (Explorer II 216570, adding Paraflex), and the date-less 3130, 3131 and 3132.
A freshly serviced Cal. 3135 should show about 270 to 310 degrees of amplitude when fully wound. More than 335 degrees can indicate that the mainspring bridle is slipping too late because it lacks braking grease; Rolex sets a minimum of 200 degrees after 24 hours in the worst position. Earlier movements carried COSC's &minus;4/+6 seconds-per-day standard. From 2015, Rolex applied its &minus;2/+2 Superlative Chronometer test to the complete watch without changing the caliber. Derivatives include Cal. 3155, 3175, 3185, 3186, 3187, and the no-date 3130, 3131, and 3132.


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== Milgauss ==
== Milgauss ==


Milgauss is Rolex's anti-magnetic line, and its two documented calibers sit half a century apart on two different base architectures — one built on the 1530-derived sport platform, the other on the modern date-less 3130 — evidence the anti-magnetic engineering gets bolted onto whatever mainstream movement is current rather than kept as its own standalone design lineage.
The two documented Milgauss calibers sit half a century apart. Cal. 1580 uses the 1530-derived sport platform, while Cal. 3131 derives from the no-date 3130. Rolex adapted the current production architecture for magnetic resistance rather than maintaining a separate Milgauss movement family.


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Powers the [[Reference:1019|Milgauss 1019]] exclusively across its entire 1960&ndash;1988 run, one of the longest single-caliber, single-reference pairings in Rolex's catalogue. It shares the 1530-derived platform with Cal. 1570 and 1575, with hacking added mid-production around 1972. The anti-magnetic engineering lives in the case rather than the movement: a soft-iron inner shield forms a Faraday cage around the caliber, which is why the 1019's case runs thicker than its Submariner and GMT-Master contemporaries built on the same movement family. Parts interchange broadly across the whole 1520/1525/1530/1535/1555/1556/1560/1565/1570/1575/1580 group.
Cal. 1580 is associated exclusively with the [[Reference:1019|Milgauss 1019]] during its 1960&ndash;1988 run, subject to the early-production dating conflict below. It shares the 1530-derived platform with Cal. 1570 and 1575, and gained hacking around 1972. A soft-iron inner shield around the movement provides the magnetic protection, making the 1019 thicker than contemporary Submariner and GMT-Master cases using the same movement family. Parts interchange broadly across the 1520/1525/1530/1535/1555/1556/1560/1565/1570/1575/1580 group.


Antiquorum's fullest description, from a New York sale in May 2004, reads: rhodium-plated, 26 jewels, straight line lever escapement, monometallic balance adjusted to 5 positions and temperature, shock-absorber, self-compensating Breguet balance-spring, Microstella regulating screws. A second Antiquorum lot from October 2005 sharpens the balance spring to "free-sprung white metal Breguet." Phillips corroborates the escapement and balance independently, cataloguing a 1019 in Hong Kong in December 2015 as a nickel lever movement, 26 jewels, mono-metallic balance &mdash; and the 26-jewel count is unanimous across Christie's, Sotheby's, Phillips and Antiquorum lots spanning 2015 to 2021. The free-sprung Microstella regulation rests on Antiquorum's wording alone; it matches the balance package Cal. 1560 and 1570 carry on the same platform, but no second house spells it out, so it should be read as strongly indicated rather than independently confirmed.
Cal. 1580 has 26 jewels, a straight-line lever escapement, a monometallic balance adjusted to temperature and five positions, shock protection, and a Breguet hairspring. Antiquorum describes the hairspring as free-sprung white metal with Microstella regulation. That matches Cal. 1560 and 1570 on the same platform, although no second auction house specifies the regulation system.


The anti-magnetic construction deserves stating precisely, because the shielding is case furniture and none of it sits inside the caliber. Every major house describes a discrete component: Antiquorum's case line for the 2004 lot reads "three-body, polished and brushed, screwed-down case back and crown, gilt metal anti-magnetic protecting cap," and Christie's, Sotheby's and Phillips all name the same gilt-metal anti-magnetic cap in their own case descriptions. Cal. 1580 itself is a standard 1530-family movement with no special metallurgy in the balance or hairspring &mdash; the ferrous cap over the movement and the inner case around it absorb the field, and the caliber inside is protected rather than immune. That is also why the 1580 could stay on the ordinary sport-caliber upgrade path, picking up hacking in 1972 alongside its siblings.
The shielding is part of the case, not the caliber. A gilt-metal anti-magnetic cap and the surrounding inner case absorb the field. Cal. 1580 itself uses the standard 1530-family balance and hairspring, so the movement is protected rather than intrinsically immune. It could therefore follow the normal sport-caliber development path and gain hacking in 1972.


One dating question stays open. The factory caliber table enters Cal. 1580 in 1963, marks it hack-after-1972, and gives its base as Cal. 1530 at 28.5 by 5.75mm and 19,800 vph &mdash; but the 1019 launched around 1960, three years earlier. The anti-magnetic calibers preceding it in that table are the 1030-family 1065M, 1066M and 1080, all entered in 1955 and all flagged anti-magnetic, and Bonhams catalogued a Milgauss 6541 on Cal. 1080 in London in December 2009 with a free-sprung Breguet balance spring of its own. Whether the earliest 1019s shipped on a 1580 or on one of those 1030-family movements is not settled by the sources here, and the claim of a single caliber across the full run should be read against that gap.
The factory caliber table introduces Cal. 1580 in 1963, three years after the 1019's generally accepted launch around 1960. It lists the earlier anti-magnetic Cal. 1065M, 1066M, and 1080 from 1955, and a Milgauss 6541 is documented with Cal. 1080. Published evidence does not settle whether the earliest 1019s used Cal. 1580 or one of these 1030-family movements.


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A date-less Cal. 3130 derivative announced at Baselworld 2007, built for the [[Reference:116400|Milgauss 116400]] and 116400GV "Glace Verte" and, from 2016, the Air-King 40 ref. 116900. Anti-magnetism runs three layers deep rather than one. Rolex's own 116400GV product page describes the first: a shield of ferromagnetic alloys inside the Oyster case surrounding the movement, carrying "the symbol for magnetic flux density – the capital letter 'B' with an arrow" engraved into it, which "only Rolex-certified watchmakers will ever see." Revolution's study of the model supplies the construction — a two-piece shield, one half screwed to the dial side of the movement and the other into the Oyster case beneath the outer caseback, with the B-and-arrow on that inner back. The second layer is the paramagnetic blue Parachrom hairspring in niobium-zirconium. The third is an escapement machined in amorphous nickel-phosphorus rather than steel, and Monochrome's history of the collection specifies both parts of it, escape wheel and pallet fork, where most write-ups name only the wheel.
Cal. 3131 is a no-date Cal. 3130 derivative announced at Baselworld 2007 for the [[Reference:116400|Milgauss 116400]] and 116400GV "Glace Verte." From 2016 it also powered the Air-King 40 reference 116900. Magnetic protection has three parts. A two-piece ferromagnetic shield encloses the movement, with one half secured on the dial side and the other beneath the outer caseback; the inner back carries a capital "B" and arrow, the symbol for magnetic flux density. The movement also uses a paramagnetic blue Parachrom hairspring and an amorphous nickel-phosphorus escape wheel and pallet fork.


The caliber went to COSC for its whole run and stayed on KIF shock protection and a conventional Swiss lever. Chronergy and Paraflex belong to the 32xx generation from 2015 and never reached it. The tightened Superlative Chronometer rating did: Rolex redefined the marking to −2/+2 seconds per day on the cased watch in 2015 and applied it across the catalogue, and both the Milgauss and the Air-King 40 were still in that catalogue — the 116900 to 2022, the 116400GV to 2023 — so late examples carry the tighter figure on a movement Rolex did not otherwise change.
Cal. 3131 remained COSC-certified throughout its run, with KIF shock protection and a conventional Swiss lever escapement. It never received Chronergy or Paraflex. Rolex applied the tighter &minus;2/+2 seconds-per-day Superlative Chronometer standard from 2015, so later 116900 and 116400GV examples carry the revised rating without a corresponding movement change. The Air-King remained in production to 2022 and the Milgauss to 2023.


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== Daytona chronograph (manual-wind) ==
== Daytona chronograph (manual-wind) ==


The manual-wind Daytona stays on Valjoux 72 architecture for its entire first chapter, 1963 through 1988, moving through five caliber numbers as Rolex progressively finished and then re-rated the same base ébauche. Valjoux was an independent Swiss ébauche manufacturer &mdash; it built the unfinished movement blank, not a complete Rolex-designed caliber &mdash; absorbed into the Ebauches SA holding group in 1944 and folded more fully into what became ETA in 1965, though movements kept the Valjoux name through the end of 72 production in 1974. Rolex was Valjoux's biggest single customer for this caliber: research into surviving case numbers puts at least 62,000 Valjoux 72/23 movements inside Rolex cases across more than 40 references, something like 7% of total Valjoux 72 output, Rolex's demand alone likely helped keep the column-wheel chronograph in production as long as it stayed viable. Heuer, Universal Genève, Longines and others built chronographs on the same base; what distinguished a Rolex example was the finishing and rate adjustment applied after the ébauche left Valjoux, not a different movement underneath.
The manual-wind Daytona used Valjoux 72 architecture from 1963 through 1988. Across five caliber numbers, Rolex progressively refinished and re-rated the same base ébauche rather than designing a separate chronograph movement.
 
Valjoux joined the Ebauches SA group in 1944 and was later folded into ETA, though the Valjoux name remained in use through the end of Cal. 72 production in 1974. At least 62,000 Valjoux 72/23 movements are recorded in Rolex cases across more than 40 references, about 7 per cent of total output. Heuer, Universal Genève and Longines also used the base. Rolex examples differ in their finishing and adjustment.


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Roughly 1955 to 1961, 17 jewels, 18,000 vph, 48 hours — the Valjoux 72 close to how it left the ébauche maker, with Rolex finishing and not much else, in the pre-Daytona ref. 6234. Bonhams catalogued a circa-1960 6234 (sale 26687, lot 14) as a "17-jewel Valjoux Cal.72 manual wind, adjusted to 3 positions, column wheel chronograph," and Antiquorum's July 2017 Geneva sale carried a 1957 example under the same bare caliber number. Rolex left the stock Valjoux regulating organ alone at this stage — index regulator, flat hairspring, factory Incabloc — the configuration Dody Giussani's text for ''Ultimate Rolex Daytona'' (Pucci Papaleo Editore) describes as the state of the movement before the Microstella balance arrived. The date band follows the 6234's own production, which Bonhams gives as 1955 to 1960 and Sotheby's as 1955 to around 1961.
Used in the pre-Daytona ref. 6234 from about 1955 to 1961, Cal. 72 remained close to the Valjoux ébauche. Rolex retained its index regulator, flat hairspring and Incabloc protection. Auction records document the bare Cal. 72 designation on examples from 1957 and around 1960; published production dates for the 6234 end in either 1960 or about 1961.


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Late 1950s to about 1961, 17 jewels, 18,000 vph, 48 hours — better documented than its reputation suggests, and the designation the major houses reach for most often on late 6234s. Sotheby's catalogued a circa-1961 example as "Valjoux cal. 72 A mechanical, 17 jewels," and a 1961 6234 with case number 688867 was listed as carrying a "manual-winding Rolex caliber 72A movement." Mechanically it is the pre-Microstella execution: Giussani's text for ''Ultimate Rolex Daytona'' describes the 72A as the version with an index regulator and a flat hairspring, both of which the 72B would replace. That makes 72A the number for a Valjoux 72 that Rolex has finished but not yet re-regulated. Sotheby's reads the ROW stamp found on many of these movements as marking a watch imported for the United States; Grail Watch Reference reads the same three letters as Rolex Werke. Neither reading has a Rolex document behind it.
Cal. 72A appears in late ref. 6234s from the late 1950s to about 1961. It retains the index regulator and flat hairspring that Cal. 72B would replace, making it a Rolex-finished but otherwise conventional Valjoux 72 execution. The meaning of the ROW stamp remains uncertain: Sotheby's associates it with US importation, while Grail Watch Reference reads it as Rolex Werke. Neither interpretation is supported by a known Rolex document.


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17 jewels, 18,000 vph, 48 hours — the execution where Rolex stops finishing the Valjoux and starts re-engineering it, in the 6238 and the last 6234s. Giussani's text for ''Ultimate Rolex Daytona'' sets out exactly what changed: the 72A's index regulator gives way to a Microstella adjustable-inertia balance, a pair of screws on the balance rim setting rate by inertia with no regulator at all, and the flat hairspring is replaced by a Breguet overcoil. Shock protection moves to KIF, often the clover-shaped Flector version. Giussani adds a period tell that has nothing to do with rate — the setting lever is screwed, so a screw beside the crown has to be loosened before the winding stem will release, a component later replaced by the pusher type.
Used in the ref. 6238 and the last 6234s, Cal. 72B marks Rolex's first substantial reworking of the Valjoux base. The index regulator gave way to a Microstella adjustable-inertia balance, the flat hairspring to a Breguet overcoil, and Incabloc protection to KIF, often in its clover-shaped Flector form. The caliber also has the earlier screwed setting lever, later replaced by a pusher type.


When the changeover happened is genuinely disputed. Giussani dates the 72B's complete replacement of the 72A to 1966; auction cataloguing runs earlier, with 6234s from around 1961 already described as 72B, and Time and Watches puts the 72B in the second-series 6238 with the 722 rename following between 1965 and 1967. On what separates 72B from 722, Giussani is unambiguous: "There are no substantial differences between the 72B and the 722 Valjoux caliber movements," and Rolex used the two names interchangeably "even on the technical documentations of the calibres." The regulating-organ swap above is the real break in this family, not the later rename.
The transition date is disputed. Dody Giussani's text for ''Ultimate Rolex Daytona'' dates the complete replacement of Cal. 72A to 1966, while auction records identify Cal. 72B in ref. 6234 examples from around 1961. Giussani finds no substantial mechanical difference between the 72B and 722 and notes that Rolex used both names in its technical documents. The change in regulating organ matters more than the later rename.


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17 jewels, 18,000 vph, 48 hours, 13 lignes across — the Rolex-stamped Valjoux 72 behind the 6239, 6240 and 6241, the run that carries the "Paul Newman" dials. Giussani describes the chronograph as a column wheel driving a horizontal clutch through a coupling yoke: a driving wheel turning with the seconds hand and permanently meshed with a setting wheel pivoted on the yoke, and pressing the start pusher swings the yoke until that setting wheel engages the chronograph centre wheel. He also names the by-product an owner sees on the dial — the engagement is abrupt enough that the chronograph hand can jump slightly forward or back at the start, which is the behaviour the vertical clutch of Cal. 4130 would eventually remove.
Cal. 722 powered the refs. 6239, 6240 and 6241, including examples with "Paul Newman" dials. Its column wheel controls a horizontal clutch through a coupling yoke. Engagement can make the chronograph hand jump slightly forward or back at the start, a trait later removed by the vertical clutch in Cal. 4130.


One stylistic detail separates a 722 from the 722-1 that followed, and Giussani is the source for it: the position of the "Rolex Genève" inscription on the plate, seen from the dial side. Beyond that the designations overlap in practice. Christie's, cataloguing a 1969 ref. 6241 in yellow gold (case no. 1'947'369), notes that the reference was produced between 1966 and 1969 and "housed either the 72B Valjoux caliber, 722 or the 722-1 variations" — which is the honest position on this family. What is engraved on a given movement tells more than any date band.
The position of the "Rolex Genève" inscription on the dial-side plate distinguishes Cal. 722 from the 722-1 that followed. The designations otherwise overlap: Christie's records Cal. 72B, 722 and 722-1 across ref. 6241 production. The engraving on the movement is more reliable than a date-based attribution.


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From 1967, 17 jewels, 18,000 vph, 48 hours, 30mm across and 6.95mm thick — the last of the 18,000 vph Daytona calibers before Cal. 727 lifted the rate. Rolex itself, per Giussani, described the 722-1 as a Valjoux 72A-based mechanism carrying the same dimensions and the same frequency as what came before, so everything that changed is internal.
Introduced in 1967, Cal. 722-1 was the last 18,000 vph Daytona caliber before Cal. 727 raised the frequency. Rolex described it as a Valjoux 72A-based mechanism with the same dimensions as its predecessor; the changes were internal.


Two changes are documented. The first is the hour-recorder conveyor, the part linking the chronograph hour wheel at six o'clock to the barrel that drives it: the new conveyor pivots on a flat eccentric screw and is pushed against the hour wheel by a wing-shaped spring in place of the 722's simpler one, the eccentric giving a watchmaker a way to set its position precisely and hold the engagement. The second is a guard spring over the balance, a metal sheet stopping the hairspring sliding across its stud support under shock. Giussani is clear that this one was already introduced on the 722 and applied inconsistently, and that it caused functional problems of its own, which is why many surviving movements of both calibers do not have it.
The hour-recorder conveyor gained an eccentric pivot and wing-shaped spring, allowing more precise engagement with the hour wheel. A guard spring above the balance was intended to keep the hairspring on its stud support under shock. Giussani records that the guard had already appeared inconsistently on Cal. 722 and caused problems of its own, so many surviving examples of both calibers lack it.


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1970–88, 17 jewels, 21,600 vph, 48 hours: the higher-beat Valjoux 72 that lifts the rate from 18,000 to 21,600 vph and runs through the 6262, 6263, 6264, and 6265 until the manual-wind Daytona era closes in 1988. The photographed comparison is a specialist side-by-side of two period movements, one catalogued as a "Rolex Daytona Ref. 6263" in quotation marks, the other a confirmed genuine 6265 with "727" plainly engraved. Specialist forensic teardown work uses the Breguet overcoil and the bevelled inner edge of the KIF shock-spring retaining ring as authentication points on this caliber specifically, distinguishing genuine examples from fakes that get the case right but not the movement detail. It doubles as a useful authentication reference generally: matching a movement's engraved caliber number against what a listing claims separates a documented example from a franken watch.
Cal. 727 raised the Valjoux 72 frequency from 18,000 to 21,600 vph and powered the refs. 6262, 6263, 6264 and 6265 from 1970 until 1988. A genuine example has a Breguet overcoil and a bevelled inner edge on the KIF shock-spring retaining ring. These details, together with the engraved caliber number, help distinguish an original movement from a substituted or counterfeit one.


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1988 to 2000, 31 jewels, 28,800 vph, chronometer — a heavily reworked Zenith El Primero 400, launched with the 16520, and the last movement in a Rolex that Rolex did not design. Sotheby's guide to the Daytona Zenith states the scale of the work directly: Rolex "reduced the beat rate to enhance durability and re-engineered over half the components." The rate change is the substantive one, from the El Primero's 36,000 vph down to 28,800, which brought the movement onto Rolex's own lubrication and service regime instead of the specialist handling a 5 Hz escapement demands. The date went. The El Primero's flat hairspring was replaced by a Breguet overcoil, and the balance became a free-sprung Glucydur wheel on Microstella screws under KIF shock protection — the oscillator Rolex had settled on with the second-generation 1500 series in the 1960s. The chronograph itself stayed conventional for its period: Giussani records the 4030 as a column wheel driving a horizontal clutch, and notes that Rolex at first declined even to acknowledge the Zenith derivation.
Launched with the ref. 16520 in 1988, Cal. 4030 was a heavily reworked Zenith El Primero 400 and the last externally designed movement used by Rolex. Rolex removed the date, reduced the frequency from 36,000 to 28,800 vph and changed more than half of the components. A Breguet overcoil replaced the flat hairspring, while a free-sprung Glucydur balance with Microstella regulation and KIF protection replaced the Zenith oscillator. The chronograph retained a column wheel and horizontal clutch.


Power reserve is where the record splits, and the split is real rather than a transcription error. Daytona Info's caliber sheet gives 54 hours; other published accounts give 52; neither figure traces to a Rolex document. The photographed example, marked "MONTRES ROLEX S.A. GENEVA SWISS, ADJ. 5 POSITIONS TEMPERATURE, THIRTY-ONE JEWELS" with "4030" in a small stamped box, confirms the caliber whichever number a given source prefers.
Published power-reserve figures split between 52 and 54 hours, with no known Rolex document settling the difference. The photographed movement is signed "MONTRES ROLEX S.A. GENEVA SWISS, ADJ. 5 POSITIONS TEMPERATURE, THIRTY-ONE JEWELS" and stamped "4030."


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2000 to 2023, 44 jewels, 28,800 vph, 72 hours, chronometer — Rolex's first chronograph of its own design, launched with the 116520. Column wheel and vertical clutch, and the clutch is the change an owner feels: where the 4030's horizontal clutch could nudge the chronograph hand at the start, this one engages cleanly. Rolex designed it for parts economy, and the figure is well attested: 201 components, which Revolution called a record low for a chronograph at the time, and which aBlogtoWatch's review of the 116520 puts in context — around 20 per cent below the El Primero-based 4030, with twelve types of screw where the 4030 ran to more than forty.
Cal. 4130 was Rolex's first chronograph movement of its own design, launched with the ref. 116520 in 2000. Its column wheel and vertical clutch provide clean chronograph engagement without the hand jump associated with Cal. 4030. The movement uses 201 components, about 20 per cent fewer than its predecessor, and twelve types of screw rather than more than forty.


The rotor turns on a ball bearing from launch rather than the plain jewelled sleeve used across the 3135 generation, a construction Chrono24's survey of the caliber portfolio credits the 4130 with establishing before it reached the 32xx movements; Caliber Corner's spec sheet records the bearing as seven balls on three screws. Descriptions of those bearings as ceramic circulate widely but trace to no Rolex or specialist source. The escapement is a conventional Swiss lever at a 52-degree lift angle, on a free-sprung balance held by a transversal bridge screwed at both ends, with KIF shock protection. Chronergy and Paraflex belong to the successor: Rolex's own 2023 Cosmograph Daytona release describes Cal. 4131 as an evolution of the 4130 that adds the patented Chronergy escapement in nickel-phosphorus, Paraflex absorbers, an optimised ball bearing and Côtes de Genève on the bridges. The same release confirms the display back as a 4131-era first and a platinum-only one — every 4130 Daytona has a solid caseback.
The rotor runs on a ball bearing rather than the jewelled sleeve used by the Cal. 3135 generation. Claims that the bearing is ceramic lack support from Rolex or specialist documentation. The free-sprung balance sits under a transversal bridge and uses KIF protection. Chronergy, Paraflex, an optimised rotor bearing and Côtes de Genève arrived with Cal. 4131 in 2023. The display back also belongs to that successor and was limited to platinum; every Cal. 4130 Daytona has a solid caseback.


Parachrom is on the caliber from launch, though the arrival of the blue anodised version specifically is not settled; published dates run from about 2005 to 2007 and none of them carries a Rolex document. Certification went through COSC, and because the caliber was still in production when Rolex tightened its Superlative marking to −2/+2 seconds per day in 2015, later examples were held to the in-house figure on an unchanged movement. It ran the entire in-house Daytona generation and continued in the 116500LN until Cal. 4131 replaced it in March 2023.
Parachrom was fitted from launch, but the blue version is variously dated between about 2005 and 2007 without a supporting Rolex document. Later examples were rated to Rolex's −2/+2 seconds-per-day standard after its introduction in 2015. Cal. 4130 continued through the ref. 116500LN until Cal. 4131 replaced it in March 2023.


<span id="day-date-family"></span>
<span id="day-date-family"></span>
== Day-Date ==
== Day-Date ==


The Day-Date runs on its own caliber family, entirely separate from the sport and Oyster Perpetual movements documented above. Quickset arrives only with the 5-digit generation — every 4-digit Day-Date sets the day and date exclusively by running the hands through midnight.
The Day-Date uses a caliber family separate from Rolex's sport and Oyster Perpetual movements. Quickset arrived with the five-digit generation; four-digit Day-Dates advance both calendar displays through the motion of the hands.


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1956–1959, 25 jewels, 18,000 vph, 42 hours — Rolex's first day-and-date caliber, carried by the originals-era 6510, 6511, 6611, 6612, and 6613. A 6511 lot description gives the whole specification in one line: "Cal. 1055, rhodium-plated, oeil-de-perdrix decoration, 25 jewels, straight line lever escapement, monometallic balance adjusted to temperatures and 5 positions, shock-absorber, free sprung, self-compensating Breguet balance spring." It is the same catalogue formula Antiquorum uses for the Cal. 1030 and Cal. 1066, and the oeil-de-perdrix ("partridge-eye") circular graining named in it is the finish to look for in place of Côtes de Genève stripes. Bonhams repeats the five-positions-and-temperature adjustment in its own words on Glasgow-import 6511s hallmarked 1956.
Cal. 1055 was Rolex's first day-and-date movement, used from 1956 to 1959 in the refs. 6510, 6511, 6611, 6612 and 6613. Its rhodium-plated bridges carry oeil-de-perdrix ("partridge-eye") circular graining rather than Côtes de Genève. Documented examples were adjusted to temperature and five positions.


Phillips dates the generational split precisely: the 6511 is replaced by the 6611 in 1957, "which features an improved caliber 1055, allowing the model to obtain a 'COSC' certification." The second-generation movement is engraved 1055B on the bridge rather than 1055, and the dial text follows the movement — "Superlative Chronometer Officially Certified" in place of the earlier "Officially Certified Chronometer" script.
The ref. 6611 replaced the 6511 in 1957 with an improved chronometer-certified version engraved 1055B on the bridge. Its dial reads "Superlative Chronometer Officially Certified" rather than the earlier "Officially Certified Chronometer."


Where the free-sprung Microstella balance enters is genuinely disputed. The standard generational account credits it to the 66xx revision, as the upgrade that earned the chronometer rating in the first place; against that, the lot description quoted above applies "free sprung" to a first-generation 6511. Both readings sit in the record and neither has been settled here. No quickset and no hacking on either generation.
The arrival of the free-sprung Microstella balance is disputed. The usual account places it with the 66xx revision, but an auction description identifies a first-generation 6511 as free-sprung. Neither generation has quickset or hacking.


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1959–c.1967, 25 jewels, 18,000 vph, 42 hours, chronometer, still non-quickset and non-hacking — the movement carrying the early 4-digit Day-Date (1803, 1804, 1806, 1807, 1811). Its parentage gets stated two ways and both are defensible: it inherits the day-and-date architecture Cal. 1055 established in 1956, and it is built on the Cal. 1530 plate already running under the sport watches. Rolex's own part numbering settles which claim carries more weight. Almost everything in a 1555 outside the calendar work is a 1530 component — balance staff 7864, pallet staff 7847, escape-wheel jewels 7937, barrel drum and arbor 7826/7827, crown and ratchet wheels 7872/7876, sliding pinion 7871, and the whole automatic-winding group from 7906 through 7919. What actually carries a 1555 number is the motion and calendar work: centre wheel 8001, cannon pinions 8002 and 8004, cam-yoke jewel 8007, cam-yoke spring 8008, calendar-wheel stud 8011. Three of those five are shared outright with Cal. 1575, the Datejust movement of the same years, so the President and the Datejust were running common calendar hardware with a day disc laid over the top.
Cal. 1555 powered early four-digit Day-Dates, including the refs. 1803, 1804, 1806, 1807 and 1811, from 1959 to about 1967. It combines the day-and-date architecture of Cal. 1055 with the plate and most running components of Cal. 1530. Its distinct parts are concentrated in the motion and calendar work, some shared with the contemporary Datejust Cal. 1575.


The escapement is the 1530's Swiss lever, unchanged, and the shock protection is KIF rather than Incabloc. Two independent lines of evidence agree: the trade parts catalogues list the upper shock spring for a 1555 under the 1530's number 7934 and label it old-type KIF, and Phillips prints "KIF flector shock absorbers" in its own cataloguing of the caliber. The balance is free-sprung with a Nivarox Breguet overcoil and Microstella regulation, no index pin bearing on the spring — the same package Cal. 1560 was carrying on the sport side from the same 1959 start. One detail here needs correcting. The Microstella components on a 1555 are screws, not the four gold nuts of the modern calibers: Rolex's own account of the system says it was screw-shaped when first developed in 1957, and Rolex's 1978 service documentation still describes screws on the successor 1556, with the changeover to nut-shaped Microstella coming only in 1983. Descriptions that put four Microstella nuts on this caliber are reading a modern balance backwards into a 1959 one.
The Swiss lever escapement comes from Cal. 1530, with KIF Flector protection rather than Incabloc. The free-sprung balance uses a Nivarox Breguet overcoil and screw-shaped Microstella adjusters. Rolex did not adopt the later nut-shaped Microstella components until 1983.


The absence of hacking shows up in the parts list rather than resting on assertion. When the 1556 gained hacking in 1972 it picked up a balance stop spring carried under Cal. 1570's number 8115; no equivalent part exists for the 1555 at all. The known weak point is the mainspring barrel bearing. The barrel arbor turns in bores cut into the main plate and barrel bridge, and after enough decades of running those bores wear out of round, the barrel tilts, and amplitude falls away; watchmakers address it by opening the worn hole and fitting a replacement bush rather than condemning a plate or a bridge. The upper barrel bush is a stocked service part for this caliber, carried under the 1530's number 7920, which is the plainest measure of how routine the repair became.
Cal. 1555 does not hack; unlike the 1972 revision of Cal. 1556, its parts list has no balance-stop spring. Wear in the mainspring-barrel bearing is a known fault. As the plate and bridge bores wear out of round, the barrel can tilt and reduce amplitude; Rolex supplied a replacement upper barrel bush for the repair.


The most closely documented 1555 in the record sits in a steel case Rolex never catalogued. Five stainless steel Day-Dates are publicly known, none of them a listed reference, and Christie's — cataloguing the fifth — sets out the census by movement number: 0004547, 0005073, DD411420, DD14749 and DD081221, the first of them published in John Goldberger's ''100 Superlative Rolex Watches'' (Damiani, 2008). The cases carry no reference and no serial, only the Rolex signature and "Stainless Steel" stamped inside the back; the day discs are French, the hands black against silvered dials, and the provenance of every known example traces to a former Rolex watchmaker. Christie's reading is that they were workshop test pieces, some handed over on retirement and some given to the Geneva horological school. Phillips sold DD411420 in Geneva in November 2019 for CHF 100,000 and pinned down what makes it more than a case curiosity: the movement is engraved 1555 but beats at 19,800 vph, the 1556's frequency, and the retiring watchmaker who received it was the man who had developed the faster beat. A caliber caught mid-development, still wearing the old number.
Five stainless-steel Day-Dates are publicly known, none with a listed reference or case serial. Christie's records movement numbers 0004547, 0005073, DD411420, DD14749 and DD081221. Their casebacks are signed Rolex and stamped "Stainless Steel"; the known examples have French day discs, black hands and silvered dials, with provenance linked to former Rolex watchmakers. Christie's identifies them as workshop test pieces. Movement DD411420 is engraved 1555 but runs at the Cal. 1556 frequency of 19,800 vph, placing it between the two generations.


Sources split on the jewel count. Antiquorum catalogues the movement at 25 jewels, matching the bridge signature, while Phillips's description of the prototype prints 26 — the 1556's figure. The rated number in either case leaves out jewels sitting in the calendar work, which is the usual explanation offered for the drift. Height grew to 7.03mm to house the day-disc mechanism, making this the thickest of the 1500 series, and the references it powered wore the stepped "pie-pan" dial profile through to about 1970, a dial-era marker that outlasts the caliber itself.
The prototype's jewel count is disputed. Antiquorum gives 25, matching the bridge signature, while Phillips gives 26, the figure for Cal. 1556. At 7.03mm, Cal. 1555 is the thickest member of the 1500 series. The stepped "pie-pan" dial remained in use until about 1970, outlasting the caliber.


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c.1965–1977/78, 26 jewels, 19,800 vph, 42 hours, chronometer, still no quickset — a higher-frequency successor to Cal. 1555, carrying the mid-and-late 4-digit Day-Date (1803, 1804, 1806, 1807, 1811). The rate went up through a gear-train change while the architecture stayed where the 1555 left it, and the twenty-sixth jewel is the one addition, at the top of the centre wheel. Rolex's own 1978 Technical and Service Information manual documents the balance directly: a screwed balance with 18 screws, including two regulating screws plus two gold star-shaped Microstella screws — a screwed balance with two-screw Microstella regulation, not the later four-nut style some secondary sources describe (Rolex only moved from screw to nut-shaped Microstella components in 1983). Full balance bridge rather than a cock, rhodium-plated with perlage finishing. Hacking was added mid-production in 1972. Monochrome's history of the Day-Date and Fratello's overview of the line both date the change to that year, and Watch Wiki records it in the same terms; examples built before 1972 do not hack. Rolex folded the change into ongoing 1556 production instead of issuing a new caliber number for it, so the hacking and non-hacking versions share one designation — a genuine running change rather than a running fault.
Cal. 1556 succeeded the 1555 around 1965 and powered the mid- and late four-digit Day-Date until 1977 or 1978. A revised gear train raised the frequency, while a jewel at the top of the centre wheel brought the count to 26. Its rhodium-plated movement has perlage finishing, a full balance bridge and a screwed balance with two gold, star-shaped Microstella regulating screws. Hacking was added during production in 1972 without a new caliber designation; earlier examples do not hack.


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The only caliber Rolex built for a single specific case: the platinum [[Reference:1831|Day-Date 1831]], commissioned for the Shah of Iran and delivered from 1977, the heaviest production Rolex ever made at 290 grams. Antiquorum's 2013 sale of example No. 05 (case 5'086'932, CHF 206,500) catalogues the movement directly: rhodium-plated, 26 jewels, straight-line lever escapement, monometallic balance adjusted to temperature and five positions, free-sprung Breguet balance spring, Microstella regulating screws, hacking. Sources disagree on how many 1831s exist — the lot's own catalogue title says eight, other researchers say nine — and on the movement itself: one concordance assigns the reference to Cal. 1556 instead of 1566, against the auction houses that physically examined the watches. Both figures are worth keeping in view rather than resolved.
Cal. 1566 was built for one case, the platinum [[Reference:1831|Day-Date 1831]] commissioned for the Shah of Iran and delivered from 1977. At 290 grams, it is the heaviest production Rolex. The rhodium-plated movement has a free-sprung Breguet hairspring, Microstella regulation and hacking. Sources record either eight or nine examples. One concordance assigns the ref. 1831 to Cal. 1556, while auction houses that examined the watches identify Cal. 1566.


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1977–1988, 27 jewels, 28,800 vph, 48 hours, hacking, chronometer — the first Day-Date caliber with any quickset at all, though only for the date; the day still advances by running the hands. Swiss lever escapement, free-sprung Glucydur balance with Microstella regulation, Nivarox Breguet overcoil, KIF shock protection on both the balance and the escape wheel. It carries a balance cock rather than a bridge — the sharpest visual contrast with Cal. 3155 below, which replaces it with a full transversal bridge. Height is commonly quoted at 6.3mm, but Rolex's own parts diagram gives 7.11mm; use the latter. Sapphire-crystal era, carrying the 18038, 18048, 18078, and early 18238. The day-disc mechanism sits visibly on the dial-side plate, distinct from the rotor-side bridge finishing shown on the earlier 1055/1555/1556 generation.
Cal. 3055 powered the refs. 18038, 18048, 18078 and early 18238 from 1977 to 1988. It introduced quickset for the date, while the day still advanced through the motion of the hands. The balance cock provides the clearest visual distinction from Cal. 3155, which uses a full transversal bridge. Common references give a height of 6.3mm, but Rolex's parts diagram specifies 7.11mm.


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1988–2019, 31 jewels, 28,800 vph, 48 hours, hacking, chronometer: adds the day quickset that Cal. 3055 lacked. Pull the crown to its first position and the same motion sets both functions in opposite directions, clockwise to advance the date and counterclockwise to advance the day, where Cal. 3055 could quickset the date alone. Grail Watch Reference and Watch Wiki both run the caliber from its 1988 launch through to 2019, replacing the 3055 in the Day-Date and outlasting every other movement in the family.
Cal. 3155 replaced the 3055 in 1988 and remained in production through 2019. It added independent correction of the day, giving the Day-Date a double quickset for both calendar displays.


The jewel count went from 27 to 31. Monochrome puts that down to the added quickset works, and Monochrome notes the movement came out slightly slimmer than the 3055 despite carrying the extra function — 6.00mm against the 3055's 6.3mm on the figures in general circulation, though 6.45mm also appears and the discrepancy has never been settled against a Rolex document. The balance is the separate 31xx-family change: Grail Watch Reference records the full balance bridge replacing the older balance cock across the generation, paired with a larger balance wheel.
The added quickset works raised the jewel count from 27 to 31. Published height figures vary between 6.00 and 6.45mm, with no known Rolex document settling the discrepancy. As elsewhere in the 31xx family, a full bridge and larger balance wheel replaced the older balance cock.


Free-sprung Glucydur balance with Microstella, Nivarox Breguet overcoil, KIF Elastor shock protection. The hairspring stud attachment changes here from glued, as on the 3035 and 3055, to laser-welded. When Parachrom arrived is disputed: Grail Watch Reference puts the update between 2008 and 2010, Watch Wiki says by 2013. Both agree on what did not happen — the 3155 kept KIF Elastor to the end and never took Paraflex, which went instead into the Cal. 3156 built for the Day-Date II. The double quickset the 18238 introduced carried the 6-digit 118238 family for three decades on the same movement.
The hairspring stud is laser-welded rather than glued as on Cals. 3035 and 3055. Parachrom arrived between 2008 and 2010 according to Grail Watch Reference, or by 2013 according to Watch Wiki. Cal. 3155 retained KIF Elastor throughout and never received Paraflex, which Rolex fitted to the Day-Date II's Cal. 3156.


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2008–2015, 31 jewels, 28,800 vph, 48 hours, hacking, double quickset, chronometer — a Cal. 3155 derivative built for the 41mm Day-Date II, with a Parachrom hairspring and Paraflex shock added, powering the 218238, 218239, 218206, and 218235. It shares its 30.97mm main plate — 2.5mm wider than the standard 28.5mm Rolex automatic, to carry an enlarged day/date wheel — with three other oversized calibers: 3132, 3136, and 3187, all built to push the date window outward in an enlarged case. Most published specs list this caliber at the standard 28.5mm, an error worth correcting on sight; the wider figure comes from Stephen Foskett's Grail Watch Reference movement database, which reads the extra flange straight off Rolex's own promotional movement photography.
Cal. 3156 is a widened Cal. 3155 derivative built for the 41mm Day-Date II from 2008 to 2015. It adds a Parachrom hairspring and Paraflex protection and powers the refs. 218238, 218239, 218206 and 218235. Its 30.97mm main plate carries the enlarged calendar wheels needed to move the date window outward. The same wider format appears on Cals. 3132, 3136 and 3187. Published specifications often give the standard 28.5mm width, but Rolex's promotional photography shows the additional flange recorded by Stephen Foskett's Grail Watch Reference.


The oversizing is confined to the plate-and-bridge layer, which is why the wrong number survives so easily. Pull a parts list for a 3156 and almost every entry carries a Cal. 3135 number — escape wheel 410, pallets 421, pallet staff 419, balance staff 429, barrel arbor 307, mainspring 311, and the whole keyless and date group — identical to what a 3155 takes. The running train and escapement of a 3156 are ordinary 31xx components dropped into a wider frame. What does not cross over is structural: trade parts listings put the barrel bridge numbered to the 3156 in a fitment group with the 3132, 3136 and 3187 rather than with the 3155, weaker evidence than a factory document but consistent with the plate width.
Only the plate-and-bridge layer is oversized. The running train, escapement, keyless works and date mechanism use standard 31xx-family components, while structural parts such as the barrel bridge are shared with the wider Cals. 3132, 3136 and 3187 rather than the 3155.


The oscillator is the 3155's, and Rolex describes it in its own terms: a large balance wheel with variable inertia regulated by gold Microstella nuts rather than an index, a Breguet overcoil, and a height-adjustable traversing bridge spanning the balance in place of a cock. Free-sprung regulation means the rate is changed by shifting mass on the balance rim, and the height-adjustable bridge lets a watchmaker set endshake without shimming, which is why Rolex ties that bridge to shock resistance rather than to timekeeping in its own copy. The escapement below it is the conventional Swiss lever the 31xx family had run since 1988. What replaced the 3156 makes the point: Cal. 3255 arrived in 2015 with the Chronergy escapement, a redrawn geometry in paramagnetic nickel-phosphorus that Rolex credits with a 15 per cent efficiency gain and with roughly half of the jump from 48 to 70 hours of reserve. The 3156 belongs to the last generation before that change, with the ferrous escape wheel and pallet fork Chronergy displaced.
The oscillator comes from Cal. 3155: a large free-sprung balance with gold Microstella nuts, a Breguet overcoil and a height-adjustable transversal bridge. Below it is the conventional Swiss lever escapement used across the 31xx family. Its 2015 successor, Cal. 3255, introduced the paramagnetic nickel-phosphorus Chronergy escapement. Rolex credits that design with a 15 per cent efficiency gain and about half of the increase from 48 to 70 hours of power reserve.


Paraflex is the one component that genuinely separates this caliber from the 3155, which kept KIF Elastor to the end of its run. Rolex filed the design on 23 March 2005 under Michel Kohler and Romain Voirol, and the European patent granted on 14 May 2008, the year the Day-Date II launched. The claim describes a shock spring tied to the bearing body by four connecting arms arranged as two suspension elements either side of a central support, against the two-armed springs the trade had used for decades. The patent's own background is unusually candid about why nobody had been working on the problem: it counts roughly 400 patents on balance-staff shock bearings, 250 of them between the early 1930s and the late 1950s, and states that the solutions then in use were broadly satisfactory, which is why the subject had almost stopped attracting new development. Rolex went back to it anyway. The published gain is up to 50 per cent more shock absorption than the KIF system it replaced — a manufacturer figure with no independent test behind it.
Paraflex is the principal component separating Cal. 3156 from the 3155, which retained KIF Elastor. Rolex filed the design in 2005, and the European patent was granted in 2008. Its spring connects to the bearing body through four arms arranged around a central support, replacing the two-arm layout common to earlier systems. Rolex claims up to 50 per cent greater shock absorption than KIF, but no independent test is cited.


This is the only Day-Date caliber whose life was bounded by a single case size. Rolex retired the Day-Date II in 2015 and replaced it with the 40mm Day-Date on Cal. 3255, while the 3155 this movement derived from carried on in the 36mm until 2019 — the derivative died four years ahead of its own base. The timing cost it one more thing: Rolex tightened the Superlative Chronometer rating to −2/+2 seconds a day in 2015, so the 3156 ran almost its entire life under the older COSC −4/+6 standard.
Cal. 3156 was confined to the 41mm Day-Date II. Rolex retired both in 2015, replacing them with the 40mm Day-Date and Cal. 3255, while the 36mm Cal. 3155 remained in production until 2019. Cal. 3156 therefore spent almost its entire run under the older COSC −4/+6 seconds-per-day standard, before Rolex adopted its −2/+2 rating in 2015.


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<span id="oysterquartz-family"></span>
== Oysterquartz ==
== Oysterquartz ==


The Oysterquartz sits outside the mechanical line entirely: Rolex's own in-house quartz calibers, launched in 1977 and run through 2001, with total output staying small — under about 25,000 watches across the full 24-year production span. Their origin traces to a genuine industry crisis: by the late 1960s Japanese quartz technology, Seiko's above all, threatened to make Swiss mechanical watchmaking obsolete almost overnight, and Rolex joined a consortium of Swiss manufacturers called the Centre Electronique Horloger (CEH) to develop a shared response. That collaboration produced the Beta 21, which powered Rolex's first quartz watch, the 1970 reference 5100 — a movement Rolex never fully embraced, since the Beta 21 architecture wouldn't fit a proper Oyster case and the 5100 shipped merely water-resistant rather than waterproof. Rolex left the CEH consortium in 1972 and spent five years developing its own quartz architecture in-house, releasing the results as cal. 5035 and 5055 in 1977, built from scratch rather than a rebadged Beta 21.
Rolex produced fewer than about 25,000 Oysterquartz watches between 1977 and 2001. The line followed the Beta 21-powered ref. 5100 of 1970, developed through the Centre Electronique Horloger consortium. The Beta 21 would not fit an Oyster case, and the ref. 5100 was water-resistant rather than waterproof. Rolex left the consortium in 1972 and spent five years developing Cals. 5035 and 5055 in-house. They were new movements, not rebadged Beta 21s.


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1977–2001, 11 jewels, hacking, quickset, chronometer, running on a single 32,768 Hz quartz crystal and a 1.55V silver-oxide cell — powers the Oysterquartz Datejust and Oyster Perpetual references, including the 17000, 17013, and 17014. Rolex's own service literature gives an overall diameter of 29.75mm, a case-fitting diameter of 29.00mm, and a height of 6.35mm, and describes the date mechanism as identical in principle to the mechanical Cal. 3035 that launched the same year.
Cal. 5035 powered Oysterquartz Datejust and Oyster Perpetual references, including the 17000, 17013 and 17014, from 1977 to 2001. Its date mechanism follows the same principle as the mechanical Cal. 3035 introduced in the same year.


Despite the popular "stepper motor" description, the drive is closer to an anchor escapement in miniature, and the factory documentation calls the assembly exactly that. Rolex's own term is a mobile-frame step-by-step motor, and what separates it from a conventional quartz stepper is that the coil moves while the magnets stay fixed, the reverse of the usual arrangement. Once a second the coil, carried on a rocking frame between the permanent magnets and the core, takes a single polarised pulse of 9.8 milliseconds and swings 45 degrees, alternating direction each beat. A finger fixed to that frame drives a pallet fork, and the fork drives the second wheel carrying the seconds hand directly at one beat per second, with the hour and minute hands geared off the same train. Movable pins on the fork lock the wheel between pulses, and a small magnet on the finger holds the fork against its banking until the next impulse arrives. The audible tick is the pallet engaging the wheel, which is why the sound reads as mechanical rather than as the hum of an ordinary quartz watch.
Rolex calls the drive a mobile-frame step-by-step motor. Unlike a conventional quartz stepper, its coil moves while the magnets remain fixed. A polarised pulse swings the coil frame once per second, and a finger on the frame drives a pallet fork connected directly to the seconds wheel. The pallet locks the wheel between pulses. Its audible tick comes from that engagement and sounds closer to a mechanical escapement than a conventional quartz motor.


The electronic module carries a C-MOS integrated circuit doing three jobs: the oscillator that sets the standard frequency in concert with the quartz and the trimmer, the binary divider that reduces 32,768 Hz to one pulse per second, and the impulse amplifier to whose terminals the motor connects. Rate is adjusted at service through a trimmer on the circuit board, turned with a dedicated Rolex screwdriver (tool ref. 2023) over a total range of about 2 seconds a day. The progression is not linear, the correction reverses once the maximum fast or slow point is passed, and a watch needing more than the trimmer can give needs a new module rather than more turns of the screw. Frequency is set to ±0.05 s/d at around 28°C.
The C-MOS module contains the oscillator, a binary divider that reduces 32,768 Hz to one pulse per second, and the motor's impulse amplifier. A trimmer provides a total adjustment range of about two seconds per day. Rolex specified regulation to ±0.05 seconds per day at about 28°C.


How the caliber handles temperature is unsettled. Secondary accounts describe the module as a thermocompensated oscillator, a VCTCXO with a thermistor reading ambient temperature and trimming the crystal's rate to suit, and the description is repeated widely enough to have become standard. Rolex's technical information for the two calibers never mentions compensation or a thermistor across its 32 pages. It prints an uncompensated parabolic rate curve instead, puts the quartz inversion point at 26 ±2°C, and instructs that movements be adjusted to the roughly 28°C of a watch on the wrist, with the rate falling away on either side of that point. The document may predate a later revision, but nothing in it supports the thermistor account, and the two have not been reconciled.
Temperature compensation remains uncertain. Secondary accounts describe a thermocompensated oscillator with a thermistor, but Rolex's technical document mentions neither. It instead shows a parabolic rate curve with an inversion point at 26 ±2°C and specifies adjustment near the 28°C temperature of a worn watch. The document may predate a later revision, but it does not support the usual thermistor claim.


Rolex did publish an accuracy figure, and it sits below the numbers usually quoted for these calibers: a gain or loss of less than one minute after a year of normal wear. Battery service life is given as over 24 months, with the whole movement drawing 9 microamps at most and the electronics alone accounting for no more than 3 of those. There is no end-of-life indication of any kind, so a dying cell announces itself through erratic running. Pulling the crown to the second catch cuts current to the motor entirely, which is why the factory instruction is to store these watches with the crown out, and why the seconds hand restarts exactly one second after the crown is pushed home.
Rolex specified accuracy within one minute per year under normal wear and battery life beyond 24 months. The movement draws no more than 9 microamps, of which the electronics use at most 3. There is no battery end-of-life indication; erratic running is the warning. Hacking cuts current to the motor, and the seconds hand restarts one second after the crown returns to its running position.


Service practice is unusually prescriptive. The electronic module, motor, printed circuit, battery bridle, battery, and date indicator are all barred from the cleaning baths, and the module is never to be washed or handled, since the oscillator and divider draw little enough current that contamination on the quartz-circuit connections alone can stop the watch. The motor's mobile-frame pivots are deliberately left dry, and its components were never sold separately, so a failed motor is replaced whole rather than repaired. Coil resistance is the test that separates a dead motor from a dead circuit, with 1,200 to 1,500 ohms the factory band.
The electronic module and motor are sensitive to contamination, and the mobile-frame pivots run dry. Rolex supplied the motor only as a complete unit rather than as separate components.


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1977–2001, 11 jewels, hacking, quickset, chronometer — the Day-Date counterpart to Cal. 5035, introduced in Rolex's own literature as a caliber derived from the 5035 whose calendar works on the same principle as the mechanical Cal. 3055. Everything in the 5035 entry about the mobile-frame motor, the C-MOS module, the trimmer and the current draw applies here unchanged, the two calibers sharing the same electronic module and the same motor as service parts. The difference is height: both measure 29.75mm across with a 29.00mm case-fitting diameter, but the 5055 stands 7.11mm tall against the 5035's 6.35mm, the extra 0.76mm going to the day-disc stack, mirroring the way the mechanical 3055 sits taller than the 3035 for the same reason.
Cal. 5055 is the Day-Date counterpart to Cal. 5035. The two share their motor and electronic module, while the 5055's calendar follows the principle of the mechanical Cal. 3055. Its day-disc stack increases the height from 6.35 to 7.11mm.


Unlike the 5035, the 5055 was COSC-certified from its 1977 launch — the 5035 only reached COSC around 1978-80, alongside a change to a tuning-fork-shaped quartz crystal, so early Oysterquartz Datejust dials lack "Superlative Chronometer Officially Certified" wording that contemporary Day-Dates already carried.
Cal. 5055 was COSC-certified from its 1977 launch. Cal. 5035 gained certification around 1978–80, alongside a change to a tuning-fork-shaped quartz crystal, so early Oysterquartz Datejust dials lack the "Superlative Chronometer Officially Certified" text found on contemporary Day-Dates.


The calendar side is where the 5055 takes on work of its own, and the factory service instructions are correspondingly fussier. Hour-wheel endshake must not exceed 0.03mm, held there by a set of four hour-wheel seats supplied in 0.02, 0.03, 0.04 and 0.05mm thicknesses. Both indicators have to fall freely when the movement is turned over, and an imperfect change is corrected at the jumper rather than the disc: strengthen the jumper's tension if an indicator overshoots, reduce it if the indicator falls short. Hands go on so that day and date change at midnight, to a tolerance of minus one to plus two minutes. Language changes were a service-counter job rather than a factory one, the day disc lifting out as its own part with a dedicated Rolex reamer for opening the centre hole when a replacement sits tight, which is how a Day-Date could be moved between the many day languages Rolex printed without disturbing the movement proper.
Cal. 5055 adds the day mechanism and its stricter tolerances. Rolex specified hour-wheel endshake below 0.03mm and calendar change within two minutes of midnight. The day disc is a separate replaceable part, allowing the display language to be changed without altering the movement.


Rolex's planned second-generation Oysterquartz calibers, 5235/5255 with a true stepper motor and 5335/5355 with a perpetual calendar, were both cancelled and never shipped in any watch. It powers the Oysterquartz Day-Date 19018 in yellow gold and 19019 in white gold, plus the pyramid-bezel 19028.
Cal. 5055 powers the yellow-gold ref. 19018, white-gold ref. 19019 and pyramid-bezel ref. 19028. Planned successors, Cals. 5235/5255 with a conventional stepper motor and 5335/5355 with a perpetual calendar, were cancelled before production.


<span id="prince-appendix"></span>
<span id="prince-appendix"></span>
== Related but not Rolex ==
== Related but not Rolex ==


Two commonly-confused calibers turn up in Prince and Bubbleback research but aren't Rolex movements at all. Gruen's Cal. 877, used in the Techni-Quadron, is the Aegler architectural sibling of Cal. 300 sold under Gruen's own brand for the US market — the shared supplier explains the identical layout, but it was never a Rolex commercial number. And any Bubbleback-era "9¾ ligne" or "9¾ lignes" note on a reference page means only that the movement's size class was documented, not the specific caliber number — a real gap in the source, not a claim that a distinct "9¾ ligne caliber" exists as its own entry.
Two commonly confused descriptions are not Rolex calibers. Gruen's Cal. 877, used in the Techni-Quadron, is an Aegler-built architectural sibling of Cal. 300 sold under Gruen's name in the United States. It was never a Rolex commercial number. A Bubbleback-era "9¾ ligne" description records only the movement's size class, not a distinct caliber designation.


== Sources ==
== Sources ==

Latest revision as of 02:21, 18 August 2026


Main Page -> Movements

Quick jump

Prince (shaped): 300 · 7½ T.S. 300 · 310 · 360 HW · 350 T.S.
Bubbleback / early automatic: 520 · 620 · 600 · A260 · A296 · 645 · 740 · 745
Oyster / Oysterdate Precision: 1210 · 1215 · 1220 · 1225
Vintage sport (1950s–80s): 1030 · 1035 · 1530 · 1560 · 1570 · 1575
Modern sport (1988–2020): 3035 · 3130 · 3135 · 3185 · 3186 · 3187
Milgauss: 1580 · 3131
Daytona chronograph: 72 · 727 · 4030 · 4130
Day-Date: 1055 · 1555 · 1566 · 3055 · 3155
Oysterquartz: 5035 · 5055

Rolex movements

The entries cover calibers tied to the Rolex families documented on this wiki, including a few poorly documented numbers with no confirmed fitment. Specifications sit alongside the history, visual details, and known reference uses. Individual reference pages carry the case-by-case fitment detail.

The caliber number is engraved on the movement itself and read with the caseback off; it is separate from the case serial, which is the number that dates the watch on the serial-number page. Where a movement number and case number diverge sharply, as on the stockpiled Prince calibers, the movement was made well before the case it sits in.

Aegler in Bienne made most of the mechanical movements covered here. The firm supplied Rolex as an independent manufacturer before becoming its subsidiary in 2004; this manufacturing relationship is separate from whether a caliber used an outside design, as the Valjoux- and Zenith-based chronographs did.

Several component technologies recur across the range. Glucydur balances, standard on Rolex automatics from the 1930s onward, use a beryllium-bronze alloy that resists magnetism and temperature-driven rate variation better than the steel balances it replaced. The name combines "glucinium," an old name for beryllium, with "dur," meaning hard. Kif shock protection, made by the Vallée de Joux firm founded in 1944, cushions the balance-staff pivots with a spring-loaded free-bearing jewel setting. Rolex's "Kif Ultraflex" and "Kif Elastor" are its versions of that system rather than separate technologies. Introduced in 2000, Parachrom is Rolex's niobium-zirconium-oxygen hairspring alloy. A blue oxide coating distinguished it from around 2005; Rolex rates it as about ten times more resistant to shock than the Nivarox alloys it replaced, as well as largely immune to magnetism and temperature changes.

Prince (shaped movements)

The Prince family uses Aegler shaped movements, older than every other Rolex caliber on this page. Wilsdorf and Aegler patented the layout in 1927 as a "shaped watch movement with a seconds dial." It placed the winding barrel at one end of the rectangular movement and the balance at the other, leaving room for a larger balance wheel and mainspring barrel than rival shaped calibers of the period. The result was better precision and a longer reserve.

Aegler remained an independent supplier until Rolex bought the company from the Borer family in April 2004. "Aegler" and "Rebberg" refer to the same firm; Rebberg was the street in Bienne where it stood. Aegler also made movements for Gruen. The architectural sibling of Cal. 300 sold in the United States as the Gruen Techni-Quadron, designated Cal. 877. Gruen-stamped movements therefore sometimes appear in Rolex Prince cases, but Cal. 877 was never a Rolex caliber number.

Prince grades run Prima → Extra Prima → Ultra Prima, with higher jewel counts, more adjustment positions, and stricter chronometer testing. Only Extra Prima and Ultra Prima watches carry "Chronometer" or "Observatory" dial marks. Rolex submitted Prince movements to the National Physical Laboratory at Kew for rate certificates independent of the Swiss Bureaux Officiels Suisse de Contrôle. Its often-cited 1914 Class A Kew certificate belongs to an earlier ladies' wristwatch movement, while Prince testing at Kew-Teddington began in 1928.

Cal. 300

Cal. 300, Extra Prima grade, rectangular Prince architecture, Bonhams lot photo
detail value
type Manual
jewels 15 (Prima) · 18 (Extra/Ultra Prima)
frequency 18,000 vph (2.5 Hz)
power reserve ~50h
size 7½ × 14½ lignes / 16.9 × 32.7mm
escapement Lateral lever
shock None

Cal. 300 is the original Prince movement, made from 1928 to 1935. Rolex's factory caliber table places it under the "T.S." size code shared by Cal. 310 and Cal. 350. Christie's describes all three as the same movement base, with interchangeable parts and the balance bridge identifying the original execution. Prima movements have 15 jewels and six-position adjustment; Extra Prima and Ultra Prima versions have 18 jewels, six-position adjustment, and sometimes a Chronometer marking. David Boettcher identifies the additional jewels as two end-stones on the escape-wheel pivots and a top bearing on the centre wheel. Early movements carry the grade wording on the ratchet wheel, while later examples place it on the main train bridge. The photographed Extra Prima, marked "Observatory 6 Positions," shows the later convention.

Balance metallurgy changed gradually. Examples from 1928 use a bimetallic balance with a plain Breguet spring; by the mid-to-late 1930s, documented movements have both monometallic and bimetallic balances paired with Elinvar-alloy hairsprings. No exact transition year is established. "Patented Superbalance" on later ratchet wheels and bridges refers to Aegler's Swiss patent CH196706, filed in August 1936 and granted in March 1938. A movement carrying the mark therefore postdates the grant. The recessed timing screws are often said to reduce air resistance, but Boettcher reads the patent as a way to maximize the balance's radius of gyration within the available space.

Cal. 300 has no shock protection, consistent with Incabloc reaching production only in 1938, after the core Prince design was established. Its winding-stem bridge is a known service weak point. A movement that sets the time and then disengages may have a broken bridge; watchmakers use aftermarket CNC-machined brass bridges and stems for this repair.

Several UK auction catalogues treat the three- and four-digit numbers found on movements in refs 1862, 1490, and 1855 as calibers. The documented numbers are 510, 579, 841, 1004, 1130, and 1439, with weaker evidence for 701 and a single record of 1759. They are almost certainly movement serials read from the plate. Continental catalogues identify the same movement class by grade and the T.S. size code instead. Cal. 414 and Cal. 527 have no documented connection to the Rolex Prince. The number 971A is a case reference, not a caliber; Antiquorum catalogued a 971A in 1989 with the same T.S./300-family movement.

Cal. 7½′′′ T.S. 300

Cal. 7½′′′ T.S. 300, marked "Rolex World's Records," "Rolex Chronometer," "18 Rubies, Ultra Prima"
detail value
type Manual
frequency 18,000 vph (2.5 Hz)
power reserve ~50h
size 7½′′′ rectangular
escapement Lateral lever
balance Monometallic
regulator Micrometer

"T.S." is Rolex's size-family code for this 16.9 × 32.7mm architecture, catalogued by Christie's as "cal. T.S. Ref. 300." There is no support for the common expansion "Très Soigné." The six-position Ultra Prima execution ran from 1932 to 1938 with a lateral lever escapement, monometallic balance, micrometer regulator, Breguet overcoil hairspring, and rhodium plating. On the 1527 Railway, Extra Prima movements outnumber Ultra Prima examples, reversing the pattern seen on the 1490. An eight-position Ultra Prima marked "Officially Tested in Eight Ways" is documented on a 1931 bamboo-bracelet example sold by Mondani in 2006.

Cal. 310

detail value
type Manual
jewels 18
size 7½′′′ rectangular (19 × 49mm cased)
escapement Lateral lever
balance Superbalance, 6-position
regulator Micrometer

Cal. 310 is the centre-seconds member of the T.S. family, used in the wedge-shaped 3361 Aerodynamic, 3362, and 3937 Prince group. Antiquorum described a 3361 in 2000 as a rhodium-plated 7½-ligne movement with 18 jewels, lateral lever escapement, six-position Superbalance, self-compensating Breguet balance spring, and micrometer regulator, in a 19 × 49mm case. That catalogue does not print the number 310, so the caliber attribution is less secure than the architecture and specifications. Movement production ended in 1938, but Aegler stock remained in Rolex cases through 1952. A 1952 example with a movement number far below its case number illustrates this stockpile pattern.

Cal. 360 HW

Cal. 360 HW, marked "Rolex, 15 Rubies, Swiss Made"
detail value
type Manual
jewels 15–18

The architecture of Cal. 360 is disputed. Christie's describes a 1938 ref. 2835 "Prince Elegant" with a tonneau-shaped 15-jewel movement, and Charles Jarman's The Rolex Reference Guide (4th edition) calls Cal. 360 a manual, small-seconds, tonneau-shaped movement with a SuperBalance. Rolex's factory caliber table instead lists a rectangular 18-jewel Basic Caliber measuring 18 × 27mm, smaller than the Cal. 300 family's 16.9 × 32.7mm.

Both Jarman and the factory table date its introduction to 1937. The disagreement concerns its shape, size, and relationship to Cal. 300. The popular claim that "HW" means Hans Wilsdorf has no independent support; the factory table appears to give the size code as "F-LW," possibly an OCR rendering related to the "F" size-family code used for Cal. 180. Shigeharu Aritake's Rolex Scene 1913–1997 is cited for a progression in which SuperBalance wording disappears from the winding wheel around 1938, but this does not resolve the architecture. Escapement and balance details therefore remain unconfirmed.

Numbered Prince movements (510, 579, 701, 841, 1004, 1130, 1439)

Seven numbers circulate as Prince "calibers": 510, 579, 701, 841, 1004, 1130, and 1439. All are most likely movement serial numbers misread as caliber designations, so they are grouped here.

Photographed Prince plates carry a grade legend, jewel count, "Swiss Made," and a bare number stamped beside the "NN RUBIES" wording, but no caliber designation. Grade legends include Prima, Extra Prima, Ultra Prima, Observatory Quality, Officially Tested in Eight Ways, Timed 6 Positions, and For All Climates. The bare number ranges from four to seven digits. Ultra Prima 18-jewel examples with otherwise matching plates carry 1260, 1439, and 1759 in that position, confirming that the stamp varies within one movement type.

Continental auction catalogues identify these movements by size code and grade, such as "cal. T.S. 300" or "7½′′′ T.S. 300, Observatory Quality." UK lots that print a "Cal." figure also give a separate case or serial number, indicating that the supposed caliber was read from the movement. The specifications also overlap: 1439 and 1759 both describe an 18-jewel Ultra Prima movement adjusted to six positions. A bare mainplate serial has likewise appeared in print as a "1240 calibre movement."

The numbers remain useful as search terms because they appear in auction descriptions. Each is listed below as a likely movement serial rather than a distinct caliber.

number documented on catalogue text notes
510 Prince Brancard ref. 1855, serial 143**, circa 1930 "17-jewel Cal.510 manual wind movement tested to 8 positions" 8-position adjustment, against the more typical 6
579 stainless steel ref. 1862, circa 1935, case No. 103 "17-jewel Cal.579 manual wind movement" (Bonhams London) single lot; the trailing "T" in some listings is absent from Bonhams' catalogue text
701 one photograph showing "ROLEX PRINCE 701" on a 1930s piece none no recorded jewel count, adjustment count, or technical description; no auction or catalogue attribution
841 ref. 1862 circa 1930, case No. 10403 "17-jewel Cal.841 manual wind" (Bonhams London; resold through Tajan in 2019, the same watch catalogued twice) a separate listing gives 15 jewels for a "Cal. 841T" on a different 1862; a caliber designation would not change jewel count
1004 ref. 1862, Glasgow import mark for 1936, serial 176** "17-jewel Cal.1004 manual wind movement tested to 8 positions" (Bonhams, December 2015) white gold bezel, fixed wire lugs, gilt brick-link bracelet
1130 9K yellow gold ref. 1490, case 30280 "cal. 1130 manual winding lever movement, 16 jewels" lowest jewel count recorded in the group
1439 Prince Chronometre ref. 1490, Glasgow import mark for 1937, serial 307** "18-jewel Cal.1439 manual wind movement timed to 6 positions" (Bonhams) same 18-jewel, 6-position Ultra Prima specification as Cal. 1759 below

Cal. 1759 is the same phenomenon. It remains separate because the photographed watch preserves matching movement and caseback markings, but the number appears in the serial position on an Ultra Prima plate and is documented in only one regional UK auction.

Cal. 1759

Cal. 1759, "1759, 18 RUBIES, ULTRA PRIMA," with its matching case back
detail value
type Manual
jewels 18

This circa 1937 Ultra Prima Chronometer has 18 jewels and six-position adjustment. Gardiner Houlgate catalogued it in a 9ct ref. 1862 with 1937 Glasgow import hallmarks as a "cal. 1759 Ultra Prima Chronometer 18 jewel movement timed 6 positions." The photographed example retains its matching caseback, engraved "1759, 18 Rubies, Ultra Prima" alongside "31 Records Universels" and a retailer stamp. The identification rests on this single regional UK auction lot.

Cal. 350 T.S.

Cal. 350 T.S., Extra Prima grade, 15 rubies, timed to 6 positions, in a ref. 1491 jumping hour
detail value
type Manual
jewels 15 or 18 (documented both ways)
size 16.9 × 32.7mm (T.S.)
escapement Lateral lever
balance Monometallic

Cal. 350 is the jump-hour member of the T.S. family, alongside the small-seconds Cal. 300 and centre-seconds Cal. 310. Christie's and Sotheby's catalogue it in the 1491 Brancard Jumping Hour as an 18-jewel, chronometer-rated movement on the T.S. base. Another 1491 has a "15 Rubies" Extra Prima movement rather than an Ultra Prima, so jewel count follows grade rather than one fixed specification. The jump-hour disc works on much the same principle as the later Datejust date disc. Surviving examples carry Glasgow import hallmarks from 1930–31, consistent with the T.S. base's 1928–35 production window.

The 1491 case is deeper than the 1490 to accommodate the jump-hour module. Case depth therefore distinguishes a genuine 1491 from a 1490 fitted with a later module. Known service faults include a weak jump-impulse spring that causes a "lazy" disc advance, a worn retention pawl that makes the hour disc jitter, and a misaligned dial aperture that exposes parts of two numerals.

Bubbleback and early automatic

Bubbleback and early Oyster Perpetual references use a distinct family of self-winding calibers. They followed the Prince's manual shaped movements and preceded the standardized post-war automatic line. The "bubble" refers to the domed caseback needed to clear the full-rotor automatic mechanism. It was not a bumper system, although many competing automatics still used one.

Cal. 520

detail value
type Automatic
jewels 19
frequency 18,000 vph (2.5 Hz)
escapement Straight-line lever
balance Superbalance

Cal. 520 debuted in the original 1933 ref. 1858 with its three-piece Oyster case. Antiquorum describes the 8¾-ligne rhodium-plated movement in a 3353 as automatic, with 19 jewels, 18,000 vph, a straight-line lever escapement, and a Superbalance with Breguet balance spring. Cal. 620 superseded it as the architecture developed through the mid-1930s. No confirmed movement photograph is available; a generic early Bubbleback movement should not be identified as a 520 unless the engraved caliber number is visible.

Cal. 620

Cal. 620, EmmyWatch
detail value
type Automatic
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 35h
size 11½ lignes / 26.4mm × 7.5mm
escapement Straight-line lever
balance Superbalance (monometallic)

Derived from the manual Cal. 600, Cal. 620 became the base for Rolex's early full-rotor automatic family. Antiquorum catalogues individual examples with 17 to 20 jewels, against the table's 17-jewel specification. Earlier 1940s movements have a swan-neck micrometer regulator without shock protection; by the early 1950s, an index regulator and shock absorber appear.

Its defining feature is a unidirectional "Perpetual" rotor that turns through 360 degrees without bumpers or buffers. The rotor is engraved "ROLEX PERPETUAL / CHRONOMETER / SWISS MADE / PATENTED / SUPER-BALANCE," while the three-screw, 18mm cover plate reads "VIS TIRETTE / PATENTED / TRIGGER SCREW." Cal. 620 powered the original 1931 "Perpetual" and early Bubblebacks. Cal. 630 and the related 635 and 645 developed from the same architecture.

Cal. 630

Cal. 630, EmmyWatch
detail value
type Automatic
jewels 17
frequency 18,000 vph (2.5 Hz)
size 26.0mm
escapement Straight-line lever
balance Monometallic

Launched in 1937, Cal. 630 was chronometer-certified under the period Swiss testing system, adjusted to seven positions, and fitted with a Breguet hairspring. One secondary source gives 18 jewels rather than the table's 17. The movement developed directly from Cal. 620 and shares its "Vis Tirette *** Patented *** Trigger Screw" cover-plate marking. Its rotor and bridge also carry the same "Rolex Perpetual Chronometer, Swiss Made, Patented, Super-Balance" signature. The caliber number stamped in the small box on the bridge distinguishes the two.

Cal. 10½ Hunter

Cal. 700, the 10½-ligne Hunter, monometallic Superbalance, shown in its Oyster case
detail value
type Manual
jewels 17–18
frequency 18,000 vph (2.5 Hz)
size 10½ lignes
escapement Straight-line lever
balance Superbalance, 6-position
regulator Swan-neck micrometer

This Aegler-supplied 10½-ligne hand-wound family uses the 700/710 architecture. It has a straight-line lever escapement, monometallic Superbalance adjusted to six positions, self-compensating Breguet balance spring, and swan-neck micrometer regulator, with no documented shock protection. The movement powers the original Air-King 4925 and its Air-Lion, Air-Tiger, and Air-Giant siblings, including the sub-seconds 4365, mid-size 4444, and 4647 Hunter Precision. Architecturally, it sits between the pre-war Prince and Bubbleback movements and the post-war automatic Cal. 1030. Rolex's factory caliber table dates Cal. 700 and 710 to 1938. It lists Cal. 720 separately as an automatic movement with shock protection, not as a third member of this manual pair.

Cal. 600

Cal. 600, manual, Super Balance — EmmyWatch
detail value
type Manual
jewels 17
frequency Not recorded
power reserve Not recorded
size 9¾ lignes / 21.7mm
escapement Not recorded — Cal. 620 derivative is straight-line lever
balance Patented Super Balance
regulator Not recorded — Cal. 620 derivative is micrometer, later index
shock None documented

Cal. 600 sits one size class below the 10½-ligne 700/710/720 family and carries a patented Super Balance. Sotheby's catalogued the movement in the Mercedes Gleitze Oyster in November 2025 as a rhodium-finished Hunter-architecture base upgraded to Cal. 600. The late-1926 27mm case belongs to the watch Gleitze wore during her 21 October 1927 Channel swim attempt and is engraved "Miss M. Gleitze / The Companion 'Oyster.' Vindication Channel Swim. October 21st. 1927."

Rolex's factory table lists Cal. 600 as a Basic Caliber: manual wind, small seconds, 21.7mm, 17 jewels, entered in 1933 under a Hunter-patent size bracket. It is the root of the 9¾-ligne automatic branch. Cal. 620 followed in 1936, with Cal. 635, 640, and 645 descending from that line in 1950. Both the factory table and Sotheby's Gleitze catalogue give 17 jewels.

The Gleitze case carries Glasgow import marks for 1926/1927, but its movement is later. Rolex's factory table dates Cal. 600 to 1933, and the stamped Super Balance refers to Aegler's Swiss patent CH196706, filed in August 1936 and granted in March 1938. The movement is therefore a service replacement fitted at least a decade after the 1927 swim. A mid-1970s Rolex service box accompanied the watch. Its historical provenance rests on the case and engraving, not on the present movement.

The escapement and regulator remain undocumented. Cal. 620, its immediate derivative, uses a straight-line lever and changes from a micrometer regulator to an index regulator, but those details cannot be assigned to Cal. 600 without direct evidence. Shock protection is more likely absent: the factory table flags it on the 1950 calibers in this branch but not on Cal. 600, whose design predates Incabloc production in 1938.

Cal. A260

Cal. A260-era movement, engraved Rolex Self Winder, Jewels, Patented
detail value
type Automatic
jewels 19
frequency 18,000 vph (2.5 Hz)
power reserve 36h
size 26.4mm
escapement Straight-line lever
balance Superbalance, blued Breguet spring
shock Present (unnamed brand)

A260 powered the first Submariner references, 6204 and 6205, from 1953 to 1955. "A.260" is Rolex's size-family code for this movement class rather than a conventional caliber number, much like "T.S." in the Prince family. Its non-butterfly rotor distinguishes it from the butterfly-rotor Cal. 1030. Hodinkee describes A260 as an adaptation of a movement used in earlier Oyster Perpetuals and later Bubblebacks, rather than a design made specifically for the Submariner.

Cal. A296

Cal. A296-era rotor component, engraved Rolex Perpetual Chronometer
detail value
type Automatic
jewels 18
frequency 18,000 vph (2.5 Hz)
power reserve 36h
size 29.5mm
escapement Straight-line lever
balance Monometallic Superbalance
regulator Index
shock Shock absorber (775-labelled lots only)

Made from 1952 to 1955, A296 powered the Big Crown 6200, early Explorers 6098, 6150 "Precision," 6298, and 6350, and early Datejusts 6104 and 6105. Its full rotor winds in one direction; it is not a bumper caliber. The 6150 and 6350 use the same movement in non-COSC and COSC forms. "A.296" is Rolex's size-family code and 775 its commercial number, so listings may use either designation for the same movement. Cal. 1030 replaced it in 1955 with bidirectional winding, a butterfly rotor, and a thinner automatic module. Phillips identifies that reduced thickness as the change that eliminated the domed Bubbleback caseback.

The movement has a straight-line lever escapement, monometallic balance, self-compensating Breguet balance spring, and index regulator. Catalogues using the commercial number 775 also specify six-position adjustment and a shock absorber, and Rolex's factory table marks ref. 775 as shock-protected. This reflects different naming conventions rather than separate builds. The same factory table assigns the A.296 size code to Cal. 765, a calendar movement with the same 29.5mm diameter and 18-jewel count, confirming that the code covers more than one commercial caliber.

Christie's describes a 6150 balance as a "patented Super-balance," linking it to Aegler patent CH196706 and the recessed timing screws used on Cal. 300. Published jewel counts vary because some catalogues separate the going train from the automatic module. Figures of 18 and 19 appear for the base movement, with another two or seven assigned to the rotor module. One 6150 is described as a 19-jewel movement with a two-jewel automatic module. The factory table's figure of 18 counts the base plate alone.

Cal. 645

Cal. 645 winding bridge, engraved "Rolex Perpetual Chronometer, Super-Balance, Patented" — EmmyWatch
detail value
type Automatic
jewels 17–20
frequency 18,000 vph (2.5 Hz)
power reserve 41h
size 26.4mm
escapement Straight-line lever
balance Superbalance, timed to 6 positions
regulator Index
shock Shock absorber

Cal. 645 belongs to the Cal. 600 family and shares the A.260 size code with Cal. 635. The distinctions are functional: Cal. 630 has sweep seconds without shock protection, Cal. 635 has small seconds with shock protection, and Cal. 645 combines sweep seconds with shock protection. Cal. 645 powered the semi-Bubbleback Oyster Perpetual refs 6084, 6085, and 6284 around 1948–1953. Auction catalogues give 17 to 20 jewels, consistent with both differing counting conventions and market-specific tariff variants found elsewhere in the family.

The movement uses a straight-line lever escapement, Superbalance adjusted to six positions, shock absorber, self-compensating Breguet balance spring, and index regulator. Some catalogues use "monometallic balance timed to 6 positions" instead of Superbalance. Both describe the same part: Superbalance is a monometallic balance with recessed timing screws, not a separate metallurgy.

Rolex's factory table gives the lineage as Cal. 600 to 635 to 645. It places Cal. 635, 640, and 645 under the A.260 size code at 26.4mm and 18 jewels, all entered in 1950 and all shock-protected. The shock system separates this 1950 A.260 group from the 1936 Cal. 620 base.

Jewel counts also vary according to whether a catalogue includes the automatic module. Bonhams describes the related Cal. 745 as "18 jewels plus 7 rotor jewels." Its 20-jewel description of a Cal. 645 in a 6085, against the factory table's 18, does not necessarily indicate a different movement.

Cal. 740

Cal. 740 in a reference 4467 Datejust, case back removed, rotor engraved "Rolex Perpetual Chronometer, Super Balance, Vis Tirette"
detail value
type Automatic
jewels 18 base plate (26 in Antiquorum lots — see note)
frequency 18,000 vph (2.5 Hz)
power reserve Not recorded
size 29.5mm
escapement Straight-line lever
balance Superbalance, adjusted to 6 positions
regulator Index (A.295-labelled lots)
shock Not named in 740 lot text

Cal. 740 powered the original Datejust ref. 4467, introduced in 1945 with Rolex's first automatic wristwatch date mechanism. It uses the 720/730 base architecture and the A.295 size code, the earlier sibling of the A.296 group.

The 10½-ligne rhodium-plated movement has a straight-line lever escapement, Superbalance adjusted to six positions, and self-compensating Breguet balance spring. Some catalogues substitute "monometallic balance adjusted to 6 positions" for Superbalance, as they do for Cal. 645. No Cal. 740 description names the regulator; the related A.295-coded movement in ref. 6075 uses an index regulator.

The jewel count differs by convention. Antiquorum gives 26, while Rolex's factory table gives 18; the higher figure likely includes the winding module, as Bonhams itemises the related Cal. 745 as "18 jewels plus 7 rotor jewels."

The production date remains unresolved. Rolex's factory table enters Cal. 740 in 1950 and its Cal. 720 and 730 bases in 1945, five years after the ref. 4467 launch. Early 4467s may have used a 720-series movement before Cal. 740 arrived, or the table date may be wrong. Published descriptions of surviving 4467s do not settle the sequence.

Shock protection is unconfirmed. The factory table flags it for Cal. 720 and 730 but not Cal. 740, and ref. 4467 catalogue descriptions do not mention a shock absorber. These omissions suggest an unprotected balance but do not prove it.

Cal. 745

Cal. 745, gilt rotor engraved "Rolex Perpetual Chronometer, Super Balance" — EmmyWatch
detail value
type Automatic
jewels 18 + 7 rotor
frequency 18,000 vph (2.5 Hz)
power reserve 42h
size 29.5mm
escapement Straight-line lever
balance Superbalance
regulator Index
shock Shock absorber

Cal. 745 adds a calendar to Cal. 740 and shares balance-staff and stem parts with the 700/710/720/730/740/760/765/775 family. Rolex's factory table assigns it the A.295 size code and a 1950 entry date. It is based on the 720–740 architecture; Cal. 740 has no calendar.

Bonhams describes a Cal. 745 in a ref. 6305 as rhodium-plated, with 18 jewels plus seven rotor jewels, a straight-line lever escapement, Superbalance, shock absorber, self-compensating blued-steel Breguet balance spring, and index regulator. Separating the base movement from the winding module explains why totals of 18, 25, and 26 appear for the same build. The blued-steel balance spring is also a period marker, preceding the white-metal springs seen later.

Cal. 745 appears in the Datejust "Ovettone" group. Documented examples include a circa 1955 18K yellow-gold ref. 6305, case 97602; a ref. 6105 with 1952 Glasgow import marks and movement H78230; and a circa 1955 ref. 6304 with movement 99698/H46452. Other ref. 6105 examples use A296, placing the reference across the boundary between the A.295 and A.296 groups. The claimed Cal. 745 fitment in ref. 6039 is unverified; no supporting lot description or confirmed Rolex ref. 6039 has been identified.

Oyster and Oysterdate Precision

Precision is Rolex's non-chronometer manual line, a 10½-ligne family built alongside the automatic Bubblebacks. The Oysterdate Precision 6694 remained in production through the end of the 1980s, a year beyond the hand-wound Daytona; one surviving lot includes a 1990/1991 Rolex calendar card. It was not the last manual-wind Rolex. The Cellini Danaos used Cal. 1602 into 2008, while the chronometer-certified Cellini Prince used Cal. 7040 from 2005 until about 2015. The small-seconds Cal. 1240 also carried this architecture into the platinum Cellinium 5240 and 5241. Seconds placement, date and beat rate distinguish the seven commercial numbers. Rolex's parts plates identify Cal. 1210 as the base for 1200, 1215, 1220, 1225 and 1240.

Cal. 1210

Cal. 1210 in a 1960 Oysterdate Precision ref. 6466, movement in case
detail value
type Manual
jewels 18 (factory plate) · 17 (as signed and catalogued)
frequency 18,000 vph (2.5 Hz)
power reserve ~58h
size 10½′′′ / Ø23.80mm × 4.27mm height
escapement Straight-line lever, jewelled pallet fork
balance Glucydur, screwed rim, Breguet overcoil
regulator Index with movable stud support
shock KIF-pattern, balance and escape wheel

Rolex's parts plates identify Cal. 1210 as the family's architectural base and file the small-seconds 1200 as a derivative. This resolves a published disagreement between Fratello, which names 1200 as the base, and Horbiter, which names 1210.

The jewel count remains unclear. Rolex specifies 18 jewels for the two no-date calibers and 17 for the date versions, yet known movements are signed "Seventeen Jewels" and major-house catalogues consistently give 17. Both counts are documented, but their distribution among watches has not been established. Contemporary American import duties taxed jewel count and also account for the "UNADJUSTED" stamps found on some movements.

The balance is Glucydur with a Breguet overcoil, as specified on the sibling Cal. 1200 plate. Regulation uses a conventional index and movable stud, with adjusting washers in five thicknesses. It is not free-sprung; Rolex reserved Microstella for its 12½-ligne chronometers.

The pallet fork runs in jewels, while the escape wheel has shock-mounted settings and cap jewels on both pivots, matching the treatment of the balance. Indirect centre seconds, driven from the fourth wheel through a friction-sprung pinion, can produce seconds-hand flutter even in a healthy movement. The earliest examples may lack shock protection; Antiquorum's 1946 ref. 4560 description names none.

Documented fitments include refs. 3745, 4560, 6420, 6422, 6426/6427, 6466, 6480, 6482, 6494, 9083 and 9659. Bonhams also records a ref. 6694 with a III.60 caseback date on Cal. 1210. Ref. 6082 is disputed: Crott assigns one example to 1210, while Antiquorum and EveryWatch catalogue the reference with Cal. 710.

Cal. 1215

Cal. 1215 in a movement holder, from a 1962 Oyster Date Precision ref. 6694 service
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve ~58h
size 10½′′′ / Ø23.80mm × 5.07mm height
escapement Straight-line lever
balance Glucydur, Breguet overcoil (via base 1210) · flat in one lot
regulator Index with movable stud support
shock KIF-pattern
date Non-quickset, dragging change

Cal. 1215 adds a calendar to the 1210, increasing movement height from 4.27mm to 5.07mm. Its two-page parts sheet covers only the calendar mechanism and defers the rest to Cal. 1210. Date discs came in champagne, silvered, and champagne with red-and-black printing.

The hairspring is disputed. The parts plates imply the 1210's Breguet overcoil because the 1215 sheet specifies no separate balance. Antiquorum describes one ref. 9996 with a flat hairspring and index regulator, but uses Breguet wording elsewhere. No catalogue describes the caliber as free-sprung.

The non-quickset date changes progressively rather than snapping at midnight. A pawl on the calendar wheel engages a star wheel beneath the date disc, moving it over roughly forty minutes before the jumper spring seats it. Rolex used the same arrangement in the 7xx, 1035 and 11xx families; instantaneous change arrived with the 1065/1066 and 15xx calibers. A date that begins moving around 11:20 is therefore operating normally.

Christie's places the ref. 6494 changeover between a circa-1956 example with Cal. 1210 and a circa-1958 example with 1215. Other documented fitments include the Speedking 6430, early 6694 production, and refs. 9996/9919. Refs. 6094 and 6294 used Cal. 740 and 790 respectively, rather than 1215.

Cal. 1216

detail value
type Manual (assumed, by family)
jewels not documented
status Number attested in the parts trade only

Almost nothing is known about Cal. 1216. The common description of it as a 17-jewel Cal. 1215 variant has no traceable support.

Rolex's surviving parts plates cover 1200, 1210, 1215, 1220, 1225 and 1240, but omit 1216. No major-house lot identifies a Rolex Cal. 1216, and Heritage's apparent example is a case reference. Confusion is also possible with Ronda's contemporary 1216 movement.

The parts trade nevertheless records it as a Rolex number. Cas-Ker's genuine-parts catalogue places 1216 between 1215 and 1220 and lists crown-wheel screw 1216.5420, following Rolex's caliber-prefixed numbering convention.

Rolex therefore appears to have designated a Cal. 1216, but its jewel count, seconds layout, beat rate and fitments remain unknown. Published specifications derived from the 1215 are unconfirmed.

Cal. 1220

detail value
type Manual
jewels 18 (factory plate) · 17 (as signed)
frequency 21,600 vph (3 Hz)
power reserve ~58h
size 10½′′′ / Ø23.80mm × 4.27mm height
escapement Straight-line lever
balance Screwless, inertia blocks, flat hairspring
regulator Index with movable stud support
shock KIF-pattern

Cal. 1220 raises the 1210 platform to 21,600 vph and uses a different oscillator. Both its parts plate and the 1978 third edition of Rolex's Technical and Service Information give that rate. The sometimes-published 19,800 vph figure is unsupported.

The higher-beat generation replaces the 1210's screwed Glucydur balance and Breguet overcoil with a smooth-rimmed balance and flat hairspring. Gilt and nickel-plated inertia blocks provide about ten seconds per day of fine adjustment across their range; the index handles larger corrections. Separate regulator, stud-support and regulating-stud parts confirm that this is an index-regulated movement, not a free-sprung one.

Cal. 1220 appears mainly in the oversize ref. 8029, but its dates conflict. Phillips gives 1950, Antiquorum dates case 714105 to about 1951, and Sotheby's dates that same case to about 1961 without naming its caliber. The earlier dates sit awkwardly beside the later-1960s siblings and remain unresolved. Claims that 1220 movements were commonly signed 1225, including those in later ref. 6426 production, are unverified.

Cal. 1225

Cal. 1225 in a ref. 6694 Oysterdate Precision, bridges marked "Montres Rolex S.A. Swiss"
detail value
type Manual
jewels 17
frequency 21,600 vph (3 Hz)
power reserve ~58h
size 10½′′′ / Ø23.80mm × 5.07mm height
escapement Straight-line lever
balance Screwless, inertia blocks, flat hairspring
regulator Index with movable stud support
shock KIF
date Non-quickset, dragging change

Cal. 1225 adds a calendar to the 1220 and carried the Oysterdate Precision 6694 through its final years. Rolex's plate specifies a timed flat hairspring with gilt and nickel-plated inertia blocks, consistent with Antiquorum's descriptions of refs. 6426 and 6694. Published claims of a Breguet overcoil conflict with the factory plate and auction record. Bonhams' reference to a "Gyromax balance" is a cataloguing error; Gyromax is Patek Philippe's free-sprung system.

None of these Precision calibers was chronometer-certified. "Precision" does not mean hand-wound: the automatic Air-King 5500 used the term with Cal. 1520 and "Super Precision" with Cal. 1530, neither certified. The "UNADJUSTED" stamp found on some 1225 movements is an import-duty declaration, not a grade.

The caliber does not hack. The 1210 parts plate contains no stop lever or hack spring, and Rolex's 1978 service book covers hacking only for the late 1500 series and the 2030/2035.

Recurring service faults include worn pendant-tube and crown threads, winding stems and mainsprings, plus water-damaged date rings. The early Oysterdate calendar is the movement's weak point, though the pallet fork is fully polished and its jewels lightly undercut. Rolex service centres still accept these calibers; one 1974 example returned from overhaul running two seconds per day with a measured 57-hour reserve.

Documented fitments include refs. 6426, 6466 and, most often, 6694 from the late 1960s through at least 1979. Comparison of a 1966 ref. 6694 with Cal. 1215 and a 1973 example with 1225 places the changeover around 1967.

Cal. 1200

Cal. 1200, bridges marked "Montres Rolex S.A. Geneva Swiss, Seventeen 17 Jewels", from a Rolex Precision service
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve ~58h
size 10½′′′ / Ø23.80mm × 3.65mm height
escapement Straight-line lever, jewelled pallet fork and staff
balance Glucydur, Breguet overcoil
regulator Index with movable stud support
shock "Rolex Shockresisting" device

Cal. 1200 is the family's small-seconds variant and, at 3.65mm, its thinnest member. Moving the seconds from the centre to a subdial requires a separate main plate and train-wheel bridge rather than an added module. The plate, bridge, third and fourth wheels, pallet fork and staff are jewelled.

The bilingual parts plate specifies Rolex's own "Shockresisting" device rather than a trade name. It lists a pivoted Glucydur balance with roller and a regulated Glucydur balance with Breguet hairspring, the 18,000-vph oscillator inherited by the 1210 and 1215.

The caliber number is engraved in the balance-wheel hub sinking rather than on a bridge or the main plate. The same document directs watchmakers to Cal. 1210 for all shared parts, confirming the family's parentage.

No major-house lot names Cal. 1200, so its fitments remain unestablished. The high-beat small-seconds Cal. 1240 is better documented in the platinum Cellinium 5240 and 5241, with a monometallic balance adjusted to four positions and a flat hairspring. That caliber kept the architecture in production for about a decade after the Oysterdate ended.

Vintage sport calibers (Submariner, GMT-Master, Explorer, Air-King)

The vintage sport line begins with the A-series and Cal. 1030, then settles into the long-running 15xx family. Cal. 1530 served the early 1960s, Cal. 1520 became the non-chronometer mainstay, and the chronometer-grade 1560 and 1570 carried Submariner, GMT-Master and Explorer production into the 1980s.

Cal. 1030

Cal. 1030, engraved "1030," 25 jewels, butterfly rotor
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h
size 28.5mm × 5.85mm
escapement Straight-line lever
balance Monometallic, blued Breguet spring
shock KIF

Produced from 1950 to 1962, Cal. 1030 was Rolex's first bidirectional and fully in-house automatic. Its 5.85mm profile ended the domed Bubbleback caseback, while the cutaway "butterfly" rotor stamped ROLEX PERPETUAL PATENTED is its clearest visual identifier. Finishing includes perlage on the rhodium-plated main plate, brushed bridges, polished screw heads and red anodized-aluminium reversing wheels. A conventional index regulates the movement; the visible regulator arm distinguishes it from the later free-sprung 1560 and 1570. Documented fitments include ref. 6098 from 1952, Submariners 6536, 6536-1 and 6538, Explorer 6610 and Air-King 6552. The same movement appeared in chronometer and non-chronometer watches.

Cal. 1035

Cal. 1035, rotor engraved "Rolex Perpetual Patented" — EmmyWatch
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h
size 28.5mm × 6.66mm
escapement Straight-line lever
balance Monometallic, temp + 5 positions
regulator Index (Cal. 1030 base)
shock Shock absorber

Cal. 1035 adds a date to the 1030 and appeared in 1957. It powered Oyster Perpetual Date refs. 6518, 6530 and 6534, plus the Datejust Thunderbird 6609. Rolex describes its non-quickset calendar as "progressive": the date moves gradually through the night, unlike the instant-change 1036 GMT.

The 1035 inherits the 1030's conventional index regulator rather than Microstella. Auction descriptions do not name the regulator, but the production dates and shared base support the index arrangement.

Rolex stamped the 1035's self-winding bridge "1030," as it also did on the 1036. This causes auction catalogues to identify the same reference under both numbers. The calendar work and 6.66mm height distinguish the 1035 from the 5.85mm no-date 1030. A correct ref. 6534 therefore contains a 1035 regardless of its bridge engraving.

Cal. 1530

Cal. 1530-era butterfly rotor halves, Rolex coronet stamped
detail value
type Automatic
jewels 17 / 25 / 26 (market variants)
frequency 18,000 vph (2.5 Hz)
power reserve 44h
size 12½′′′
escapement Swiss lever, club-tooth
balance Screwed Glucydur
regulator Index (coarse) + micro-star fine-adjust screws
shock KIF Flector

Cal. 1530 ran from 1957 to 1965. Its 17-, 25- and 26-jewel versions are concurrent market variants, not a chronological progression. Seventeen-jewel movements appear in a 1958-era ref. 5508, a 5500 and a 1011 Eaton, and Rolex's 1978 service booklet still treats low-jewel 1520 and 1530 movements as current configurations.

Cal. 1530 is the base for the 1520, 1560, 1570 and 1580. They share plates and many service parts, including interchangeable automatic-device bridges, so the engraved bridge number may not identify the movement beneath it. Balance-bridge and regulator form are more reliable. Cal. 1030, not 1530, was Rolex's first fully in-house automatic.

Regulation combines an index for coarse adjustment with two pairs of micro-star fine-adjustment screws on the outer balance rim. Turning a screw clockwise draws it inward and gains rate. The system resembles Microstella, and Horotec lists the same adjustment tool for the 1530 and later Microstella calibers, but Rolex reserved the Micro-Stella name for its free-sprung 12½-ligne chronometer movements. The 1530 retains an index.

The form-1 balance cock uses KIF Flector; forms 3 and 4 use Elastor, with form 2 also assigned to Flector by specialist comparisons. Interchangeable bridges mean an individual movement's shock setting may not match its engraved caliber number.

The hairspring remains disputed. Antiquorum consistently describes a Breguet overcoil and index regulator, while much of the reference literature gives a flat hairspring with stick regulation. Reliable sources support both descriptions.

Chronometer status also varies. Sotheby's describes the 1530 as uncertified, while Phillips and Christie's identify chronometer examples in the 5504 family. Rare 5512 and 5508 watches with four-line chronometer dials and Cal. 1530 have been reported, though no major-house lot confirms them. Certification appears to have been occasional. The Microstella-equipped 1555 and 1560 became the regular chronometer alternatives used in early refs. 1675 and 1016.

The rotor changed from butterfly to half-moon during production. Later movements also gained blued automatic-bridge screws and coloured reversing wheels in place of brass-coloured gears. Rolex describes the red wheel finish as a hardening treatment for aluminium introduced in 1957; collector descriptions often call the wheels purple and Teflon-coated. Rotor and reversing-wheel form help date an example.

The 1530 first entered the Submariner in ref. 5508, followed by 5510; neither was chronometer-rated at launch. It replaced the 10-series in non-chronometer watches, including Precision models, the Air-King, ref. 5504 "Super-Precision" Explorer and the Canadian Explorer-Date with Cal. 1535. Certified models such as the 6542 GMT, 6610 Explorer, Datejust and Day-Date retained 10xx calibers for longer. Strongly documented fitments include refs. 5508, 5510, 5512, 5513, 5500 and 5504. Single-lot support exists for 5501, 5502, 5506, 5516 and 5590/1011 Eaton. Bonhams listings for refs. 1002 and 1003 are internally inconsistent and remain unconfirmed.

Rolex specifies a 0.122–0.125mm mainspring for the 18,000-vph 1530 and 1560, against up to 0.125 or 0.128mm for the higher-beat 1520 and 1570. Early unjewelled barrel-bridge arbor holes can wear; Rolex prescribed closing the hole or reaming it for a jewel, while later production received a bushing. Rotor-axle wear is another known fault. On the 1560, a hard shock could push the hairspring into the regulator. Rolex supplied a safety pin free of charge and later made it standard, so both guarded and unguarded examples are correct.

Cal. 1520

Cal. 1520, engraved "1520," EmmyWatch
detail value
type Automatic
jewels 17 / 25 / 26
frequency 19,800 vph (2.8 Hz)
size 12½′′′
escapement Straight-line lever
balance Monometallic, screwless, flat hairspring
regulator Index (coarse) + two inertia blocks
shock KIF

Produced from 1963 to 1990, Cal. 1520 is the non-chronometer, higher-beat derivative of the 1530. Rolex pairs the 18,000-vph 1530 with the 1560, and the 19,800-vph 1520 with its certified counterpart, the 1570.

Rolex describes regulation by an index and two inertia blocks, one gilt and one nickel-plated, on a screwless balance with a flat hairspring. Turning their splits inward slows the movement and outward gains rate, with about ten seconds per day across the adjustment range. The index handles coarse changes. This differs from both the 1530's micro-star screws and the 1570's free-sprung Microstella system.

The regulating system, rather than hairspring form, separates the certified calibers from the rest of this family. Rolex used free-sprung Microstella regulation in its 12½-ligne chronometers, while the 1520 retained an index and inertia blocks.

The rim weights can be mistaken for a free-sprung system, but factory documentation confirms the regulator and inertia blocks. Two Bonhams descriptions call the 1520's balance "free-sprung Gyromax," an error that applies Patek Philippe's trademark to an index-regulated Rolex movement.

Auction descriptions consistently give a flat hairspring, apart from one 2013 Antiquorum outlier that says Breguet. Shock protection is KIF in Flector or Elastor form, identified by balance-bridge and regulator shape. That shape is more reliable than the engraved caliber number because bridges interchange across the series.

The 17-, 25- and 26-jewel counts are concurrent market variants. The 17-jewel version uses a different main plate and bridges, altered escape-wheel pivot geometry, and bushings in place of jewels in the automatic module. The going train and balance are unchanged, so jewel count does not affect timekeeping. Dated examples place 17- and 26-jewel movements together from the mid-1960s, with 25-jewel examples running alongside them.

American tariffs rose sharply above 17 jewels, but Rolex did not document this as the reason for the low-jewel version. Seventeen-jewel movements also reached Europe and Asia, so general cost reduction remains another possibility. The American presentation ref. 7002 has a rotor marked "SEVENTEEN JEWELS" and "UN" for unadjusted, both relevant to the tariff schedule, but this does not settle the question.

Documented fitments include the 5513, 5514 COMEX, 5517 military Submariner, 5500 Air-King and 5520. Ref. 1002 uses chronometer calibers 1530 or 1570; apparent 1520 examples are ref. 5500 cases with 1002 stamped inside the caseback. Ref. 5501 remains unconfirmed. Hacking arrived as a running change around 1972 through parts 8073 and 8074. Two lines above six o'clock identify the non-chronometer dial, against four on certified models.

The barrel bridge and arbor hole are known wear points. Rolex prescribed closing a worn hole or reaming it for a 2.30mm jewel; a later beryllium bushing largely solved the problem. Rotor axles and autowinder wheels also wear, and replacement parts are scarce. Gritty manual winding is normal because the reversers run without lubrication.

Cal. 1535

Cal. 1535, EmmyWatch
detail value
type Automatic
jewels 26
frequency 18,000 vph (2.5 Hz)
power reserve 42h
size 28.5mm
escapement Swiss lever
balance Monometallic, screwed
regulator Index, pre-Microstella
shock Shock-absorber

Cal. 1535 is the non-chronometer date version of the 1530, introduced in 1957 for the Air-King-Date 5700/5701. Rolex's factory caliber table places it before the later 1520-based Cal. 1525, consistent with the production dates. Monochrome likewise assigns both calibers to the 5700, with 1535 first.

Auction houses usually catalogue refs. 5700 and 5701 under the base caliber. Antiquorum assigns a 1963 ref. 5700 to Cal. 1530 and a 1972 example to 1520, though neither base movement has a date. Read as family shorthand, those entries match Rolex's parts catalogues, which file 1535 components with the 1530 and 1525 components with the 1520. They support the lineage but do not confirm the exact caliber number.

The table's mechanical figures derive from the 1530 base because no auction lot identifies a 1535 directly. Evidence for the hairspring conflicts: auction wording gives a flat spring, while Rolex balance assembly 7855 for the 1530 uses a Breguet overcoil. Repeated catalogue boilerplate is more likely than a separate variant. The 1535 predates Microstella and uses an index with a screwed balance, consistent with the 5700's Precision grade.

Although Cal. 1530 was phased out by 1965, its 1535 date derivative remained in the Air-King-Date into the late 1980s.

Cal. 1525

Cal. 1525, EmmyWatch
detail value
type Automatic
jewels 17 / 25
frequency 19,800 vph (2.8 Hz)
power reserve 42h
size 28.5mm
escapement Swiss lever
balance Monometallic, flat hairspring
regulator Index
shock Shock-absorber

Cal. 1525 is the higher-beat, non-chronometer date version of the 1520. Introduced in 1965, it carried the Air-King-Date 5700/5701 through later production. Contemporary chronometer-rated Oyster Perpetual Date references used a related 1500-series caliber instead.

Auction catalogues often identify this movement by its 1520 base rather than the 1525 date variant. Antiquorum does so on a 1972 ref. 5700, while describing the expected flat hairspring and index-regulated architecture. The chronometer-grade 1560 and 1570 use a Breguet overcoil and Microstella; the 1525's simpler regulating organ suits the 5700's Precision grade.

Jewel counts of 17, 25 and 26 reflect parallel market executions rather than separate variants. Rolex balance-assembly numbers confirm a flat hairspring for the 1520 and 1525, against a Breguet spring on the 1530 and Microstella on the 1560. The 1525 remains index-regulated.

Cal. 1560

Cal. 1560, EmmyWatch
detail value
type Automatic
jewels 26 (25 in some lot descriptions)
frequency 18,000 vph (2.5 Hz)
power reserve 42h (secondary sources only)
escapement Straight-line lever
balance Free-sprung monometallic, Microstella screws
shock KIF (pattern not named in lots)

Cal. 1560 arrived in 1959 as the chronometer-grade 15xx movement, with a free-sprung balance adjusted to temperature and five positions. Auction catalogues give both 25 and 26 jewels without establishing a pattern. Antiquorum usually describes a Breguet overcoil; its flat-hairspring description for one ref. 1502/1503 is an outlier.

Microstella regulation, rather than jewel count, separates the 1560 from the 1530. Its free-sprung balance has no index. Watches made from 1959 to 1965 were tested by the Bureaux Officiels de Contrôle de la Marche des Montres, usually under collective certificates and to a standard around −1/+10 seconds per day in five positions. COSC did not exist until September 1973, so describing an early 1560 as COSC-certified is anachronistic.

Factory balance 7980 serves the 18,000-vph chronometer group: 1555, 1556, 1560 and 1565. Later replacement part 8106 and balance bridge 8102 span both 18,000- and 19,800-vph family members, so a serviced 1560 may carry the later balance. Documented fitments include the four-line 5512, 5504 and Explorer 1016. The GMT-Master 1675 instead used the 1565 to about the 1.4-million serial range and the 1575 thereafter. Family-wide bridge engravings explain 1675 movements marked 1560 or 1570; a base 1560 lacks both calendar and 24-hour works. Although 1570 became the new fitment in 1965, 1560 movements appear in Explorers until about 1967.

Cal. 1565

Cal. 1565, EmmyWatch
detail value
type Automatic
jewels 25–26 (sources disagree)
frequency 18,000 vph (2.5 Hz)
power reserve 44h
escapement Straight-line lever
balance Free-sprung, Microstella
shock KIF

Produced from 1959 to 1965, Cal. 1565 is the early ref. 1675's "caller" GMT movement: its 24-hour hand remains linked to the main hour hand rather than independently adjustable. Rolex kept that layout until Cal. 3085. The 1565 introduced a free-sprung Breguet overcoil with Microstella regulation to this lineage, replacing the index used by earlier sport calibers.

Cal. 1570

Cal. 1570, open caseback
detail value
type Automatic
jewels 26
frequency 19,800 vph (2.8 Hz)
power reserve 48h
size 12.5′′′ (28.2mm)
escapement Straight-line lever
balance Free-sprung monometallic, four Microstella screws
shock KIF (Flector or Elastor)

Cal. 1570 is the 19,800-vph revision of the 1560, introduced in 1965. It retains the free-sprung Breguet overcoil and Microstella regulation, with adjustment to temperature and five positions. Family-wide bridge engraving causes date movements such as the 1575 in a ref. 1665 to appear marked 1570; the engraving alone does not identify the exact caliber.

The balance has four Microstella screws in two opposing pairs, not two. Rolex required equal adjustment within each pair to preserve poise. The larger pair changes rate by about two seconds per day and the smaller by about one. On this family the screws sit in the balance rim; the later 3135 platform moves its Microstella nuts to the inner rim.

KIF's circa-1972 material catalogue lists Flector and Elastor settings for Rolex, not Ultraflex. Auction catalogues name only a shock absorber, while Rolex part 8065 serves the upper balance setting across the 1520, 1530, 1560 and 1570. Flector and Elastor are therefore the supported patterns.

Hacking appeared gradually around 1971–72, with timing varying by model. Cal. 3035 began replacing the 1570 in new production from 1977, but the Explorer 1016 retained it until 1988–89. The documented diameter is 12.5 lignes, or 28.2mm; the often-published 28.5mm is a rounded conversion. Published heights conflict.

Cal. 1575

Cal. 1575, EmmyWatch
detail value
type Automatic
jewels 26 (25 per Ashton Tracy)
frequency 19,800 vph (2.8 Hz)
power reserve 48h
escapement Straight-line lever
balance Free-sprung monometallic, Microstella screws (1570 balance)
shock KIF (Flector or Elastor)

Cal. 1575 adds calendar work to the 1570; the GMT execution also adds a 24-hour train. Antiquorum and Sotheby's give 26 jewels, while watchmaker Ashton Tracy's 2018 Quill & Pad study gives 25. Tracy records a 48-hour power reserve; the often-published 50-hour figure lacks support.

Rolex engraved the 1575 bridge "1570," so that marking on a ref. 1680 or 1675 identifies the family rather than the exact caliber. Factory parts records distinguish 1565G, 1575, 1575G and 1575GMT. Date and GMT versions are separately catalogued builds, and the GMT parts also circulated as a conversion set for a standard 1560 or 1570.

The 1575 shares factory balance assembly 8106 with the 1570 and related family members. It also has escape-wheel shock protection on both dial and movement sides, not only on the balance. Documented fitments include the Submariner 1680, GMT-Master 1675 from about the 1.4-million serial range, Explorer II 1655 and Sea-Dweller 1665.

GMT-Master line

The GMT branch developed in three steps. Cal. 1036 and 1065 belong to the bakelite-bezel 6542 era, with the 24-hour hand synchronized to the main hour hand. Cal. 1565, 1575, and 3075 retained that "caller" layout through the 1675 and 16750 generations. Cal. 3085 introduced the independently jumping local hour hand, while Cal. 3175 kept the synchronized layout in the 16700 until 1999 alongside the Cal. 3185 and 3186 used in the 16710.

Cal. 1036

Cal. 1036, EmmyWatch
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h (secondary sources only)
escapement Straight-line lever (inferred, 1030 base)
balance Monometallic (inferred, 1030 base)
shock KIF (inferred)

Cal. 1036 is Rolex's first GMT movement, a Cal. 1030 with a 24-hour train added for the bakelite-bezel 6542. It runs at 18,000 vph and was chronometer certified. The 6542 used Cal. 1036 first, followed by 1065 and 1066 during its 1955–1959 production run. Its period chronometer certificate came from the Bureaux Officiels; COSC did not exist until 1973.

The start year remains disputed. Phillips dates the 6542's release to 1954, Hodinkee starts production in 1955, and Rolex registered the GMT-Master name on 21 April 1955. An announcement in 1954 followed by sales in 1955 would reconcile those dates, but Rolex has not documented that sequence.

The escapement, balance, and shock protection in the table are inherited from the Cal. 1030 base rather than documented on a Cal. 1036. Auction catalogues seldom identify a 6542 movement as Cal. 1036, so those three specifications remain provisional.

Cal. 1065

Cal. 1065, EmmyWatch
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h (secondary sources only)
escapement Straight-line lever (inferred, 1030 base)
balance Monometallic (inferred, 1030 base)
shock KIF (inferred)

Cal. 1065 is the mid-run 6542 caliber. Multiple Phillips lots identify it as an automatic movement with 25 jewels, the same jewel count recorded for the Cal. 1066 that followed.

Its dates are less secure than its specification. Cal. 1065 sits second in the 6542's three-movement sequence and is generally dated to 1957, but no factory document or dated lot fixes the transition. The 42-hour power reserve is also a secondary-source figure.

The escapement, balance, and shock rows likewise derive from the Cal. 1030 base. Cal. 1066 cataloguing supports that family relationship, but these details have not been documented directly on a Cal. 1065.

Cal. 1066

Cal. 1066, stamped "1066," butterfly rotor engraved "Rolex Perpetual Patented," EmmyWatch
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h

Cal. 1066 was the third and final movement fitted to the 6542, replacing Cal. 1065 for the last two years of production. It runs at 18,000 vph with 25 jewels and about 42 hours of reserve. Antiquorum describes a straight-line lever escapement, monometallic balance adjusted to temperature and five positions, shock absorber, and self-compensating Breguet hairspring. Its matching descriptions for Cal. 1030 and 1065 support a shared base with GMT work added.

The regulator and balance specification remain uncertain. Cal. 1030 descriptions name an index regulator, while Cal. 1066 descriptions omit it; one 6542 is catalogued with a free-sprung Glucydur balance. This may mark a running change or inconsistent cataloguing. A circa-1959 Phillips example directly confirms the Cal. 1066's butterfly rotor.

Documented examples cluster in 1958 and 1959, including a steel 6542 with a IV.1958 caseback and two gold watches dated to 1959. Rolex changed caliber numbers during the reference's run, so two outwardly similar 6542s can carry different movements.

Cal. 3075

Cal. 3075, engraved "3075," EmmyWatch
detail value
type Automatic
jewels 27
frequency 28,800 vph (4 Hz)
power reserve 48h
escapement Straight-line lever
balance Free-sprung monometallic, Microstella screws
balance support Balance cock (3035 generation)
shock KIF (inferred; lots record only "shock absorber")

Cal. 3075 carried the synchronized "caller" GMT layout into the 16750 generation. It has 27 jewels, a straight-line lever escapement, a monometallic balance adjusted to temperature and five positions, a free-sprung Breguet hairspring regulated by Microstella screws, hacking, and quickset. The quickset advances only the date wheel.

The balance is monometallic, not Glucydur. Catalogue descriptions identify Microstella screws but do not record their count, material, or position on the rim. They also name a shock absorber without identifying its maker, so the KIF attribution remains inferred from Rolex practice of the period.

The 3075 belongs to the 3035 generation and uses its cantilevered balance cock. Cal. 3175 and 3185 later introduced a balance bridge anchored at both ends. Its start date is disputed: the 16750 did not appear in a Rolex catalogue until 1981, while Antiquorum dates production of the 16758 to 1979. Known fitments are the steel 16750, steel-and-gold 16753, and gold 16758. The 3075 also moved the GMT hand above the hour hand, reversing the Cal. 1575 stack; later GMT calibers retained that arrangement.

Cal. 3085

Cal. 3085, EmmyWatch
detail value
type Automatic
jewels 27
frequency 28,800 vph (4 Hz)
power reserve 48h
size 28.5mm × 6.3–7.2mm (sources disagree)
escapement Swiss lever
balance Free-sprung, Microstella
shock KIF (per published specs, unconfirmed)

Cal. 3085 ran from 1983 to 1989 on the Cal. 3035 platform, with 27 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification. It was the first Rolex caliber to separate the local-hour hand from the 24-hour hand. The crown jumps the local hour forward or backward in one-hour steps without disturbing the minutes, seconds, or home-time hand. The date advances only by cycling the local-hour hand, so the movement has no direct quickset date.

Published thickness figures conflict. Grail Watch Reference gives 6.3mm, while Caliber Corner gives 7.2mm against the Cal. 3185's 6.45mm. This matters because the thicker movement and case produced the 16760's "Fat Lady" and "Sophia Loren" nicknames. Cal. 3085 appeared only in the 16760 GMT-Master II and 16550 Explorer II. Published specifications agree on a Breguet hairspring and Microstella regulation, but KIF shock protection has not been confirmed by an auction description or Rolex document.

Cal. 3175

Cal. 3175, EmmyWatch
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
escapement Swiss lever
balance Free-sprung Glucydur, Microstella
balance support Balance bridge (3135 generation)
shock KIF Elastor (3100-family text, not lot-confirmed)

Cal. 3175 ran from 1988 to 1999 with 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, and chronometer certification. Auction descriptions confirm the jewel count and adjustment to temperature and five positions. The free-sprung Glucydur balance, Microstella regulation, Breguet hairspring, and KIF Elastor setting come from published 3100-family specifications rather than a Cal. 3175 lot. KIF Elastor is therefore probable, not directly confirmed.

Architecturally, Cal. 3175 is a Cal. 3135 with a fixed 24-hour hand. It uses the 3135's balance bridge, anchored at both ends, where Cal. 3075 used a cantilevered cock. The 24-hour hand remains linked to the local hour hand, so a second time zone is read from the rotating bezel. The 16700 kept this synchronized layout while the rest of the line moved to the jumping-hour Cal. 3185.

Cal. 3175 appeared only in the 16700 and was Rolex's last fixed GMT movement. Reports of factory Cal. 3185 fitment in late 16700s rest on a contradictory parts listing and a rebuilt watch; documented Cal. 3185 fitment belongs to the 16710. Sotheby's has incorrectly described Cal. 3175 as having an independent GMT hand. The accepted 16700 production span is 1988–1999, although Fratello gives 2001 in one account. The 1997 change from tritium to Super-LumiNova affected the dial, not the movement.

Cal. 3185

Cal. 3185, engraved "3185"
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 6.45mm
balance Free-sprung Glucydur, four Microstella nuts

Cal. 3185 ran from 1989 to about 2007. Derived from Cal. 3135 with added 24-hour work, it has 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, chronometer certification, and KIF Elastor shock protection. It powered the 16710, 16713, 16718, and 16570, replacing Cal. 3085 in the GMT-Master II and Explorer II.

The balance carries four Microstella nuts arranged as two opposing pairs of different sizes. Rolex's Microstella wrench instructions require equal adjustment of both nuts in a pair to preserve the balance-wheel poise. Adjusting one without its opposite puts the wheel out of poise.

At 6.45mm, Cal. 3185 is slimmer than the Cal. 3085 it replaced, allowing the 16710 to sit flatter than the "Fat Lady" 16760. Its practical identification tell is visible during setting: the 24-hour hand twitches slightly as the local hour jumps. Cal. 3186 removed that play, so the test distinguishes the two without opening the case.

Cal. 3186

Cal. 3186, engraved "3186"
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 50h
size 28.5mm × 6.45mm
escapement Swiss lever
balance Monometallic, free-sprung
regulator Microstella screws, no index
shock Shock-absorber, pre-Paraflex

Cal. 3186 ran from 2007 to 2019. It added a Parachrom hairspring to the Cal. 3185 base while retaining 31 jewels, a 28,800 vph frequency, hacking, quickset, and chronometer certification; reserve increased to 50 hours. It powered late 16710 production and the ceramic-bezel 116710LN, 116710BLNR, and 116719BLRO.

The movement has a straight-line lever escapement, monometallic balance adjusted to temperature and five positions, shock protection, a free-sprung Breguet-form hairspring, Microstella regulation, and hacking. One Antiquorum description calls the hairspring blued steel, but Cal. 3186 uses Parachrom, a niobium-zirconium alloy coloured by an oxide layer rather than tempering.

Cal. 3186 retains the Cal. 3135 architecture used by the 3185: 28.5mm diameter, 6.45mm height, 28,800 vph, and 31 jewels. It also keeps the plain-bearing oscillating-weight axle, part 568, shared with Cal. 3130, 3135, 3155, and 3175. Once lubricant migrates, the axle wears and requires replacement and riveting at service.

Rolex introduced Cal. 3186 as a running change, leaving its start date unsettled. Steel 16710 examples begin among late Z- and M-series cases; the lowest documented example is Z 5786xx, but higher Z-series watches can still contain Cal. 3185. Gold references changed earlier. A D-series 116718 catalogued with Cal. 3186 was sold in August 2006, placing the movement in production before the commonly cited 2007 steel transition.

Both Cal. 3185 and 3186 index the local-hour hand with a jumping-hour click. Cal. 3186 reworked the parts and reduced slack between the drive-train wheels. As a result, the 24-hour hand twitches when the local hour jumps on a 3185 but remains still on a 3186. This identifies the caliber without removing the caseback.

The jumping-hour click spring is the caliber's known failure point. A failed spring lets the local-hour hand glide instead of indexing in one-hour steps and can leave it loose on its wheel. Rolex superseded part 657 first with 657-1 and then 657-2; the later springs are stronger and slightly larger. The fault is documented across the 16710, 16570, 116710, 116713, 116718, and 116719, as well as Cal. 3187. It does not normally damage other components, but the hour-jump action should be checked on an unserviced watch.

Cal. 3187

Cal. 3187, official Rolex photo, engraved "3187," blue Parachrom hairspring, free-sprung Microstella balance
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48–50h (sources disagree)
size 30.97mm (contested; 28.5mm also published)
escapement Swiss lever
balance Monometallic, free-sprung
regulator Microstella screws, no index
shock Paraflex

Cal. 3187 is an enlarged Cal. 3186, widened to move the date window outward in the 42mm Explorer II case. It powered only the 216570 from 2011 to 2021, before Cal. 3285 replaced it in the 226570. The Parachrom hairspring, Breguet overcoil, and independently adjustable local-hour hand carry over from the GMT lineage. Paraflex is new here, replacing the KIF Elastor used by Cal. 3185 and making Cal. 3187 the first movement in this family with Rolex's own shock system.

Cal. 3187 uses a larger baseplate and reworked surrounding parts but retains the Cal. 3186 regulating organ: a straight-line lever escapement, free-sprung monometallic balance under a full bridge, and Microstella regulation without an index. Auction catalogues confirm 31 jewels but do not itemize those inherited components.

Rolex launched the 216570 and Cal. 3187 together in March 2011 for the Explorer II's fortieth anniversary. The 42mm case required the larger movement, while the orange 24-hour hand recalled the 1655. Both remained in production until 2021, and no other reference used the caliber.

Two documented unit commissions use Cal. 3187. A 2012 white-dial 216570 made for members of the British Special Air Service carries "Who Dares Wins," the winged-dagger badge, and its owner's identifiers. A circa-2015 example numbered 40/48 was made for the UK Attack Helicopter Force. These were unit commissions rather than ministry-issued watches and should not be classified with the 5513 MilSub.

Cal. 3187 inherited the 3186's jumping-hour click-spring failure. On affected watches, the local-hour hand glides instead of indexing in one-hour steps. Rolex revised the part twice, and serviced examples may carry the later, stronger spring.

The −2/+2 rating applies only after Rolex redefined Superlative Chronometer in 2015. Earlier watches carried the COSC −4/+6 seconds-per-day standard for the uncased movement; later examples were tested again by Rolex as complete watches. The underlying caliber did not change beyond regulation.

Modern sport calibers (1988–2020)

The modern time-only line begins with Cal. 3000, the first 28,800 vph no-date movement of the period, followed by Cal. 3130 and 3132. The date-equipped Cal. 3135 reached the Submariner two years earlier and remained Rolex's main date movement through three decades of Submariner Date production.

Cal. 3000

Cal. 3000
detail value
type Automatic
jewels 27
frequency 28,800 vph (4 Hz)
power reserve 42h (48h in some sources)
size 28.5mm × 5.8mm
balance Adjustable-mass, flat hairspring

Cal. 3000 is the no-date member of the 3000 family, used from about 1990 to 2001 in the Air-King 14000 and 14010, Submariner 14060, and Explorer 14270. The often-quoted 1988 start belongs to Cal. 3135. The Air-King changed to reference 14000M in 2000, while the Explorer became the 114270 and the Submariner adopted Cal. 3130 in 2001. Published power-reserve figures conflict at 42 and 48 hours; no Rolex figure settles the difference.

Cal. 3000 was Rolex's last movement without a Breguet overcoil. It uses a flat hairspring, unlike the outgoing 1570 generation and the rest of the 3000 family. Rate is set by Microstella adjustment rather than an index, the hairspring is glued to the balance stud, and shock protection is KIF. COSC certification used the standard −4/+6 seconds-per-day tolerance.

Cal. 3035

Cal. 3035, engraved "3035," EmmyWatch
detail value
type Automatic
jewels 27
frequency 28,800 vph (4 Hz)
power reserve 48h
balance Free-sprung, four Microstella screws
shock KIF Elastor

Cal. 3035 ran from 1977 to 1988 in the 16800, 168000, 16808, and 16803. It was the first quickset Submariner caliber, with 27 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification. Compared with the Cal. 1570 generation, it increased frequency from 19,800 vph and added a crown position that advances the date wheel directly. Its free-sprung Nivarox Breguet overcoil is regulated by four Microstella screws and protected by KIF Elastor.

Two construction details separate it from Cal. 3135. Its balance sits on a cantilevered cock rather than a bridge anchored at both ends, and its hairspring is glued to the stud rather than laser-welded.

Cal. 3130

Cal. 3130, engraved "3130," EmmyWatch
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 28.5mm × 5.85mm
escapement Swiss lever
balance Monometallic Glucydur, free-sprung
regulator Microstella screws, no index
shock KIF Elastor

Cal. 3130 is the time-only successor to Cal. 3000, used in the 14060M, 114060, 114270, and 114200. It brought a full balance bridge, a larger balance wheel, and a Breguet overcoil hairspring. Rolex's parts sheet identifies Cal. 3135 as the base and gives 28.5mm diameter, 5.85mm height, 28,800 vph, and 31 jewels. Published introduction dates range from 1999 to 2001; the precise year remains unsettled.

Cal. 3000 supports its balance from a cock anchored on one side; the 3130 uses a bridge secured at both ends, which stabilizes endshake under lateral shock. Its Glucydur balance is free-sprung, with rate set by Microstella nuts rather than an index. KIF Elastor shock protection distinguishes it from the Paraflex-equipped Cal. 3132. At 5.85mm it is 0.15mm thinner than Cal. 3135 because it omits the date mechanism. The main plate is the dedicated part 3130-100, although some smaller components retain 3135 part numbers.

The 14060M initially used Cal. 3130 without COSC certification and carried a two-line dial. Certification arrived in late 2007, adding the two-line "Superlative Chronometer Officially Certified" inscription. The movement itself did not change.

The main wear point is the oscillating-weight axle, Rolex part 568, shared with Cal. 3135, 3155, 3175, and 3185. It runs in a plain sleeve bearing rather than a ball bearing. Once lubricant migrates, axle wear can produce rotor play and fine reddish dust. Replacing and riveting the axle is a routine service repair.

Cal. 3131, announced in 2007, adapts the 3130 for magnetic resistance with a blue Parachrom hairspring, a paramagnetic nickel-phosphorus escapement, and a two-part soft-iron shield around the movement. It powered the Milgauss 116400 and 116400GV, then the Air-King 116900.

Cal. 3132

Cal. 3132
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 30.97mm (contested; 28.5mm also published)
escapement Swiss lever
balance Monometallic Glucydur, free-sprung
regulator Microstella screws, no index
shock Paraflex

Cal. 3132 powered the Explorer 214270 from 2010 to about 2020. It is a Cal. 3130 with a Parachrom hairspring and Paraflex shock protection, retaining 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, and chronometer certification.

The base architecture remains a straight-line lever escapement with a free-sprung Glucydur balance under a full bridge, Microstella regulation, and no index. Paraflex replaced the 3130's KIF Elastor settings; Rolex claimed up to 50 per cent greater shock resistance. The blue Parachrom hairspring replaced Nivarox with a paramagnetic niobium-zirconium alloy whose colour comes from a patented oxide treatment.

Cal. 3132 brought Parachrom and Paraflex to the time-only professional line. Parachrom had appeared in Cal. 4130 in 2000, but the Submariner did not receive both features until Cal. 3230 in 2020.

Both dial generations of the 214270 use Cal. 3132. The 2016 revision lengthened the hands and added luminous filling to the 3, 6, and 9 numerals, without changing the movement. Cal. 3132 also retains the 3130's plain-bearing oscillating-weight axle, which wears after its lubricant migrates.

Rolex redefined Superlative Chronometer in 2015, changing the guaranteed rate from COSC's −4/+6 seconds per day on the uncased movement to −2/+2 on the cased watch after additional in-house testing. The movement did not change, so early and late 214270 examples carry different rate guarantees.

Cal. 3135

Cal. 3135, official Rolex photo, engraved "3135," 31 jewels
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 28.5mm
escapement Swiss lever
balance Free-sprung Glucydur, four Microstella nuts
regulator Free-sprung, no index
shock KIF (never Paraflex)

Cal. 3135 ran from 1988 to 2021 with 31 jewels, a 28,800 vph frequency, 48 hours of reserve, hacking, quickset, and chronometer certification. It powered the 16610, 16613, and 16618 through the 116610 generation. The Submariner changed to Cal. 3235 with the 126610 on 1 September 2020, but the Oyster Perpetual Date 34 references 115200 and 115234 kept Cal. 3135 in production into 2021. Later end dates conflate it with Cal. 3131. The movement has rhodium plating, bevelled and polished screws, and a two-piece axle-style bidirectional rotor.

The conventional Swiss lever escapement is paired with a free-sprung Glucydur balance. With no index or curb pins, four Microstella nuts on the inside of the rim set the rate by changing the wheel's inertia. Older 1530-family balances place their adjustment screws on the outside. Cal. 3135 uses a Breguet overcoil and laser-welds the hairspring to its stud, replacing the glued joint used by Cal. 3035.

The main architectural change from Cal. 3035 is the balance bridge. Part 3135-120 is secured at both ends and carries height-adjusting nuts, keeping the pivots aligned under load and allowing endshake adjustment without shims. It also prevents the hairspring from fouling a cantilevered balance cock, a known Cal. 3035 problem. Cal. 3135 increased the jewel count from 27 to 31 and uses a larger balance wheel.

Cal. 3135 used KIF shock protection throughout its run and never received Paraflex. Rolex assigned new caliber numbers to Paraflex versions: 3130 became 3132, 3155 became 3156, and 3186 became 3187. The larger Paraflex date movement for the Datejust II was Cal. 3136. A 16610 or 116610 described as having Paraflex is therefore misidentified.

Parachrom arrived during the Cal. 3135 run, but the transition date is unsettled. The niobium-zirconium alloy receives a uniform anodised oxide layer about 50 nanometres thick, which gives the hairspring its blue colour and stabilizes its restoring torque. Published dates for its adoption in Cal. 3135 range from about 2005 to 2009, with transitional examples reported on both sides. The ceramic-bezel 116610 uses it consistently from 2010. The spring's colour is therefore only a rough dating marker.

Two wear points sit in the automatic works. The anodised purple-red reversing wheels, part 3135-540, are visible through the rotor cutout and identify the movement without disassembly. Failure produces free rotor spin without winding or gritty manual winding. Epilame belongs across the reverser assembly, while oil is confined to the arbor and bearing points; oil on the teeth or clicks can jam the mechanism. The oscillating-weight axle, part 3135-568, runs in a plain jewelled sleeve. Wear causes a rattle, rotor contact with the caseback, and red dust in the movement. Rolex supplied mainsprings in standard part 3135-311 and weaker 3135-311-1 versions, a relevant distinction when assessing a rebuilt movement.

A freshly serviced Cal. 3135 should show about 270 to 310 degrees of amplitude when fully wound. More than 335 degrees can indicate that the mainspring bridle is slipping too late because it lacks braking grease; Rolex sets a minimum of 200 degrees after 24 hours in the worst position. Earlier movements carried COSC's −4/+6 seconds-per-day standard. From 2015, Rolex applied its −2/+2 Superlative Chronometer test to the complete watch without changing the caliber. Derivatives include Cal. 3155, 3175, 3185, 3186, 3187, and the no-date 3130, 3131, and 3132.

Milgauss

The two documented Milgauss calibers sit half a century apart. Cal. 1580 uses the 1530-derived sport platform, while Cal. 3131 derives from the no-date 3130. Rolex adapted the current production architecture for magnetic resistance rather than maintaining a separate Milgauss movement family.

Cal. 1580

Cal. 1580, marked "26 Jewels, Adjusted Six 6 Positions" — EmmyWatch
detail value
type Automatic
jewels 26
frequency 19,800 vph (2.8 Hz)
power reserve 48h
size 28.5mm × 5.75mm
escapement Straight-line lever
balance Free-sprung monometallic, Microstella screws
regulator None — free-sprung
shock Shock absorber

Cal. 1580 is associated exclusively with the Milgauss 1019 during its 1960–1988 run, subject to the early-production dating conflict below. It shares the 1530-derived platform with Cal. 1570 and 1575, and gained hacking around 1972. A soft-iron inner shield around the movement provides the magnetic protection, making the 1019 thicker than contemporary Submariner and GMT-Master cases using the same movement family. Parts interchange broadly across the 1520/1525/1530/1535/1555/1556/1560/1565/1570/1575/1580 group.

Cal. 1580 has 26 jewels, a straight-line lever escapement, a monometallic balance adjusted to temperature and five positions, shock protection, and a Breguet hairspring. Antiquorum describes the hairspring as free-sprung white metal with Microstella regulation. That matches Cal. 1560 and 1570 on the same platform, although no second auction house specifies the regulation system.

The shielding is part of the case, not the caliber. A gilt-metal anti-magnetic cap and the surrounding inner case absorb the field. Cal. 1580 itself uses the standard 1530-family balance and hairspring, so the movement is protected rather than intrinsically immune. It could therefore follow the normal sport-caliber development path and gain hacking in 1972.

The factory caliber table introduces Cal. 1580 in 1963, three years after the 1019's generally accepted launch around 1960. It lists the earlier anti-magnetic Cal. 1065M, 1066M, and 1080 from 1955, and a Milgauss 6541 is documented with Cal. 1080. Published evidence does not settle whether the earliest 1019s used Cal. 1580 or one of these 1030-family movements.

Cal. 3131

Cal. 3131 from a Milgauss 116400GV, auto bridge and gold reversing wheels
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 28.5mm
escapement Nickel-phosphorus escape wheel & pallet fork
balance Free-sprung monometallic, Microstella
shock KIF

Cal. 3131 is a no-date Cal. 3130 derivative announced at Baselworld 2007 for the Milgauss 116400 and 116400GV "Glace Verte." From 2016 it also powered the Air-King 40 reference 116900. Magnetic protection has three parts. A two-piece ferromagnetic shield encloses the movement, with one half secured on the dial side and the other beneath the outer caseback; the inner back carries a capital "B" and arrow, the symbol for magnetic flux density. The movement also uses a paramagnetic blue Parachrom hairspring and an amorphous nickel-phosphorus escape wheel and pallet fork.

Cal. 3131 remained COSC-certified throughout its run, with KIF shock protection and a conventional Swiss lever escapement. It never received Chronergy or Paraflex. Rolex applied the tighter −2/+2 seconds-per-day Superlative Chronometer standard from 2015, so later 116900 and 116400GV examples carry the revised rating without a corresponding movement change. The Air-King remained in production to 2022 and the Milgauss to 2023.

Daytona chronograph (manual-wind)

The manual-wind Daytona used Valjoux 72 architecture from 1963 through 1988. Across five caliber numbers, Rolex progressively refinished and re-rated the same base ébauche rather than designing a separate chronograph movement.

Valjoux joined the Ebauches SA group in 1944 and was later folded into ETA, though the Valjoux name remained in use through the end of Cal. 72 production in 1974. At least 62,000 Valjoux 72/23 movements are recorded in Rolex cases across more than 40 references, about 7 per cent of total output. Heuer, Universal Genève and Longines also used the base. Rolex examples differ in their finishing and adjustment.

Cal. 72

Valjoux 72 ébauche, caliber "72" stamped at 6 o'clock beside the Valjoux logo, plate marked "Seventeen 17 Jewels Unadjusted," stock index regulator with F/A–S/R scale — the untouched configuration Rolex fitted as Cal. 72. This example's chronograph bridge is signed Heuer-Leonidas SA
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 48h
escapement Swiss lever
shock Incabloc

Used in the pre-Daytona ref. 6234 from about 1955 to 1961, Cal. 72 remained close to the Valjoux ébauche. Rolex retained its index regulator, flat hairspring and Incabloc protection. Auction records document the bare Cal. 72 designation on examples from 1957 and around 1960; published production dates for the 6234 end in either 1960 or about 1961.

Cal. 72A

detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 48h
escapement Swiss lever
shock Incabloc

Cal. 72A appears in late ref. 6234s from the late 1950s to about 1961. It retains the index regulator and flat hairspring that Cal. 72B would replace, making it a Rolex-finished but otherwise conventional Valjoux 72 execution. The meaning of the ROW stamp remains uncertain: Sotheby's associates it with US importation, while Grail Watch Reference reads it as Rolex Werke. Neither interpretation is supported by a known Rolex document.

Cal. 72B

Rolex-signed Valjoux 72-family movement, seventeen jewels — caliber sub-variant not distinguishable from the engraving alone
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 48h
escapement Swiss lever
balance Microstella, adjustable inertia
shock KIF (often Flector)

Used in the ref. 6238 and the last 6234s, Cal. 72B marks Rolex's first substantial reworking of the Valjoux base. The index regulator gave way to a Microstella adjustable-inertia balance, the flat hairspring to a Breguet overcoil, and Incabloc protection to KIF, often in its clover-shaped Flector form. The caliber also has the earlier screwed setting lever, later replaced by a pusher type.

The transition date is disputed. Dody Giussani's text for Ultimate Rolex Daytona dates the complete replacement of Cal. 72A to 1966, while auction records identify Cal. 72B in ref. 6234 examples from around 1961. Giussani finds no substantial mechanical difference between the 72B and 722 and notes that Rolex used both names in its technical documents. The change in regulating organ matters more than the later rename.

Cal. 722

Rolex-signed Valjoux 72-family movement, seventeen jewels — caliber sub-variant not distinguishable from the engraving alone
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 48h
escapement Swiss lever
balance Microstella, adjustable inertia
shock KIF (often Flector)

Cal. 722 powered the refs. 6239, 6240 and 6241, including examples with "Paul Newman" dials. Its column wheel controls a horizontal clutch through a coupling yoke. Engagement can make the chronograph hand jump slightly forward or back at the start, a trait later removed by the vertical clutch in Cal. 4130.

The position of the "Rolex Genève" inscription on the dial-side plate distinguishes Cal. 722 from the 722-1 that followed. The designations otherwise overlap: Christie's records Cal. 72B, 722 and 722-1 across ref. 6241 production. The engraving on the movement is more reliable than a date-based attribution.

Cal. 722-1

Rolex-signed Valjoux 72-family movement, seventeen jewels — caliber sub-variant not distinguishable from the engraving alone
detail value
type Manual
jewels 17
frequency 18,000 vph (2.5 Hz)
power reserve 48h
balance Microstella (inherited from 722)
shock KIF

Introduced in 1967, Cal. 722-1 was the last 18,000 vph Daytona caliber before Cal. 727 raised the frequency. Rolex described it as a Valjoux 72A-based mechanism with the same dimensions as its predecessor; the changes were internal.

The hour-recorder conveyor gained an eccentric pivot and wing-shaped spring, allowing more precise engagement with the hour wheel. A guard spring above the balance was intended to keep the hairspring on its stud support under shock. Giussani records that the guard had already appeared inconsistently on Cal. 722 and caused problems of its own, so many surviving examples of both calibers lack it.

Cal. 727

Cal. 727 (right, engraved 727, Daytona ref 6265), specialist comparison photo via Perezcope
detail value
type Manual
jewels 17
frequency 21,600 vph (3 Hz)
power reserve 48h
escapement Swiss lever
balance Microstella, adjustable inertia
shock KIF

Cal. 727 raised the Valjoux 72 frequency from 18,000 to 21,600 vph and powered the refs. 6262, 6263, 6264 and 6265 from 1970 until 1988. A genuine example has a Breguet overcoil and a bevelled inner edge on the KIF shock-spring retaining ring. These details, together with the engraved caliber number, help distinguish an original movement from a substituted or counterfeit one.

Daytona chronograph (automatic)

Cal. 4030

Cal. 4030, engraved 4030, thirty-one jewels
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 52–54h (sources disagree)
balance Free-sprung Breguet
escapement Swiss lever

Launched with the ref. 16520 in 1988, Cal. 4030 was a heavily reworked Zenith El Primero 400 and the last externally designed movement used by Rolex. Rolex removed the date, reduced the frequency from 36,000 to 28,800 vph and changed more than half of the components. A Breguet overcoil replaced the flat hairspring, while a free-sprung Glucydur balance with Microstella regulation and KIF protection replaced the Zenith oscillator. The chronograph retained a column wheel and horizontal clutch.

Published power-reserve figures split between 52 and 54 hours, with no known Rolex document settling the difference. The photographed movement is signed "MONTRES ROLEX S.A. GENEVA SWISS, ADJ. 5 POSITIONS TEMPERATURE, THIRTY-ONE JEWELS" and stamped "4030."

Cal. 4130

Cal. 4130 movement detail, bridge marked "4130"
detail value
type Automatic
jewels 44
frequency 28,800 vph (4 Hz)
power reserve 72h
escapement Swiss lever, 52° lift angle
balance Free-sprung, four gold Microstella nuts
shock KIF

Cal. 4130 was Rolex's first chronograph movement of its own design, launched with the ref. 116520 in 2000. Its column wheel and vertical clutch provide clean chronograph engagement without the hand jump associated with Cal. 4030. The movement uses 201 components, about 20 per cent fewer than its predecessor, and twelve types of screw rather than more than forty.

The rotor runs on a ball bearing rather than the jewelled sleeve used by the Cal. 3135 generation. Claims that the bearing is ceramic lack support from Rolex or specialist documentation. The free-sprung balance sits under a transversal bridge and uses KIF protection. Chronergy, Paraflex, an optimised rotor bearing and Côtes de Genève arrived with Cal. 4131 in 2023. The display back also belongs to that successor and was limited to platinum; every Cal. 4130 Daytona has a solid caseback.

Parachrom was fitted from launch, but the blue version is variously dated between about 2005 and 2007 without a supporting Rolex document. Later examples were rated to Rolex's −2/+2 seconds-per-day standard after its introduction in 2015. Cal. 4130 continued through the ref. 116500LN until Cal. 4131 replaced it in March 2023.

Day-Date

The Day-Date uses a caliber family separate from Rolex's sport and Oyster Perpetual movements. Quickset arrived with the five-digit generation; four-digit Day-Dates advance both calendar displays through the motion of the hands.

Cal. 1055

Cal. 1055, period parts-catalogue illustration, front and back
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h
escapement Straight-line lever
balance Monometallic
shock KIF

Cal. 1055 was Rolex's first day-and-date movement, used from 1956 to 1959 in the refs. 6510, 6511, 6611, 6612 and 6613. Its rhodium-plated bridges carry oeil-de-perdrix ("partridge-eye") circular graining rather than Côtes de Genève. Documented examples were adjusted to temperature and five positions.

The ref. 6611 replaced the 6511 in 1957 with an improved chronometer-certified version engraved 1055B on the bridge. Its dial reads "Superlative Chronometer Officially Certified" rather than the earlier "Officially Certified Chronometer."

The arrival of the free-sprung Microstella balance is disputed. The usual account places it with the 66xx revision, but an auction description identifies a first-generation 6511 as free-sprung. Neither generation has quickset or hacking.

Cal. 1555

Cal. 1555, rotor bridge detail
detail value
type Automatic
jewels 25
frequency 18,000 vph (2.5 Hz)
power reserve 42h
size 7.03mm
escapement Swiss lever (Cal. 1530 train)
balance Free-sprung beryllium-bronze, Microstella screws
shock KIF Flector

Cal. 1555 powered early four-digit Day-Dates, including the refs. 1803, 1804, 1806, 1807 and 1811, from 1959 to about 1967. It combines the day-and-date architecture of Cal. 1055 with the plate and most running components of Cal. 1530. Its distinct parts are concentrated in the motion and calendar work, some shared with the contemporary Datejust Cal. 1575.

The Swiss lever escapement comes from Cal. 1530, with KIF Flector protection rather than Incabloc. The free-sprung balance uses a Nivarox Breguet overcoil and screw-shaped Microstella adjusters. Rolex did not adopt the later nut-shaped Microstella components until 1983.

Cal. 1555 does not hack; unlike the 1972 revision of Cal. 1556, its parts list has no balance-stop spring. Wear in the mainspring-barrel bearing is a known fault. As the plate and bridge bores wear out of round, the barrel can tilt and reduce amplitude; Rolex supplied a replacement upper barrel bush for the repair.

Five stainless-steel Day-Dates are publicly known, none with a listed reference or case serial. Christie's records movement numbers 0004547, 0005073, DD411420, DD14749 and DD081221. Their casebacks are signed Rolex and stamped "Stainless Steel"; the known examples have French day discs, black hands and silvered dials, with provenance linked to former Rolex watchmakers. Christie's identifies them as workshop test pieces. Movement DD411420 is engraved 1555 but runs at the Cal. 1556 frequency of 19,800 vph, placing it between the two generations.

The prototype's jewel count is disputed. Antiquorum gives 25, matching the bridge signature, while Phillips gives 26, the figure for Cal. 1556. At 7.03mm, Cal. 1555 is the thickest member of the 1500 series. The stepped "pie-pan" dial remained in use until about 1970, outlasting the caliber.

Cal. 1556

Cal. 1556
detail value
type Automatic
jewels 26
frequency 19,800 vph (2.8 Hz)
power reserve 42h
escapement Swiss lever, 52° lift angle
shock KIF Flector, both balance pivots

Cal. 1556 succeeded the 1555 around 1965 and powered the mid- and late four-digit Day-Date until 1977 or 1978. A revised gear train raised the frequency, while a jewel at the top of the centre wheel brought the count to 26. Its rhodium-plated movement has perlage finishing, a full balance bridge and a screwed balance with two gold, star-shaped Microstella regulating screws. Hacking was added during production in 1972 without a new caliber designation; earlier examples do not hack.

Cal. 1566

detail value
type Automatic
jewels 26
escapement Straight-line lever
balance Monometallic, free-sprung Breguet spring

Cal. 1566 was built for one case, the platinum Day-Date 1831 commissioned for the Shah of Iran and delivered from 1977. At 290 grams, it is the heaviest production Rolex. The rhodium-plated movement has a free-sprung Breguet hairspring, Microstella regulation and hacking. Sources record either eight or nine examples. One concordance assigns the ref. 1831 to Cal. 1556, while auction houses that examined the watches identify Cal. 1566.

Cal. 3055

Cal. 3055, period parts-catalogue illustration with day-disc
detail value
type Automatic
jewels 27
frequency 28,800 vph (4 Hz)
power reserve 48h
escapement Swiss lever
balance Free-sprung Glucydur, Microstella
shock KIF

Cal. 3055 powered the refs. 18038, 18048, 18078 and early 18238 from 1977 to 1988. It introduced quickset for the date, while the day still advanced through the motion of the hands. The balance cock provides the clearest visual distinction from Cal. 3155, which uses a full transversal bridge. Common references give a height of 6.3mm, but Rolex's parts diagram specifies 7.11mm.

Cal. 3155

Cal. 3155, engraved "3155," EmmyWatch
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
balance Free-sprung Glucydur, Microstella
shock KIF Elastor

Cal. 3155 replaced the 3055 in 1988 and remained in production through 2019. It added independent correction of the day, giving the Day-Date a double quickset for both calendar displays.

The added quickset works raised the jewel count from 27 to 31. Published height figures vary between 6.00 and 6.45mm, with no known Rolex document settling the discrepancy. As elsewhere in the 31xx family, a full bridge and larger balance wheel replaced the older balance cock.

The hairspring stud is laser-welded rather than glued as on Cals. 3035 and 3055. Parachrom arrived between 2008 and 2010 according to Grail Watch Reference, or by 2013 according to Watch Wiki. Cal. 3155 retained KIF Elastor throughout and never received Paraflex, which Rolex fitted to the Day-Date II's Cal. 3156.

Cal. 3156

Cal. 3156, engraved "3156," Day-Date II official brochure image
detail value
type Automatic
jewels 31
frequency 28,800 vph (4 Hz)
power reserve 48h
size 30.97mm
escapement Swiss lever, 31xx family (pre-Chronergy)
balance Parachrom hairspring (3155 base)
regulator Free-sprung, gold Microstella nuts, traversing bridge
shock Paraflex

Cal. 3156 is a widened Cal. 3155 derivative built for the 41mm Day-Date II from 2008 to 2015. It adds a Parachrom hairspring and Paraflex protection and powers the refs. 218238, 218239, 218206 and 218235. Its 30.97mm main plate carries the enlarged calendar wheels needed to move the date window outward. The same wider format appears on Cals. 3132, 3136 and 3187. Published specifications often give the standard 28.5mm width, but Rolex's promotional photography shows the additional flange recorded by Stephen Foskett's Grail Watch Reference.

Only the plate-and-bridge layer is oversized. The running train, escapement, keyless works and date mechanism use standard 31xx-family components, while structural parts such as the barrel bridge are shared with the wider Cals. 3132, 3136 and 3187 rather than the 3155.

The oscillator comes from Cal. 3155: a large free-sprung balance with gold Microstella nuts, a Breguet overcoil and a height-adjustable transversal bridge. Below it is the conventional Swiss lever escapement used across the 31xx family. Its 2015 successor, Cal. 3255, introduced the paramagnetic nickel-phosphorus Chronergy escapement. Rolex credits that design with a 15 per cent efficiency gain and about half of the increase from 48 to 70 hours of power reserve.

Paraflex is the principal component separating Cal. 3156 from the 3155, which retained KIF Elastor. Rolex filed the design in 2005, and the European patent was granted in 2008. Its spring connects to the bearing body through four arms arranged around a central support, replacing the two-arm layout common to earlier systems. Rolex claims up to 50 per cent greater shock absorption than KIF, but no independent test is cited.

Cal. 3156 was confined to the 41mm Day-Date II. Rolex retired both in 2015, replacing them with the 40mm Day-Date and Cal. 3255, while the 36mm Cal. 3155 remained in production until 2019. Cal. 3156 therefore spent almost its entire run under the older COSC −4/+6 seconds-per-day standard, before Rolex adopted its −2/+2 rating in 2015.

Oysterquartz

Rolex produced fewer than about 25,000 Oysterquartz watches between 1977 and 2001. The line followed the Beta 21-powered ref. 5100 of 1970, developed through the Centre Electronique Horloger consortium. The Beta 21 would not fit an Oyster case, and the ref. 5100 was water-resistant rather than waterproof. Rolex left the consortium in 1972 and spent five years developing Cals. 5035 and 5055 in-house. They were new movements, not rebadged Beta 21s.

Cal. 5035

Cal. 5035, engraved "5035," "11 ELEVEN JEWELS," "1.55V," EmmyWatch
detail value
type Quartz
jewels 11
frequency 32,768 Hz crystal
drive Mobile-frame step-by-step motor, pallet fork, 1 beat/s
circuit C-MOS module: oscillator, binary divider, impulse amplifier
rate adjustment Trimmer, about 2 s/d total range
battery 1.55V silver-oxide, 24+ months
size 29.75mm diameter (29.00mm case-fitting), 6.35mm high

Cal. 5035 powered Oysterquartz Datejust and Oyster Perpetual references, including the 17000, 17013 and 17014, from 1977 to 2001. Its date mechanism follows the same principle as the mechanical Cal. 3035 introduced in the same year.

Rolex calls the drive a mobile-frame step-by-step motor. Unlike a conventional quartz stepper, its coil moves while the magnets remain fixed. A polarised pulse swings the coil frame once per second, and a finger on the frame drives a pallet fork connected directly to the seconds wheel. The pallet locks the wheel between pulses. Its audible tick comes from that engagement and sounds closer to a mechanical escapement than a conventional quartz motor.

The C-MOS module contains the oscillator, a binary divider that reduces 32,768 Hz to one pulse per second, and the motor's impulse amplifier. A trimmer provides a total adjustment range of about two seconds per day. Rolex specified regulation to ±0.05 seconds per day at about 28°C.

Temperature compensation remains uncertain. Secondary accounts describe a thermocompensated oscillator with a thermistor, but Rolex's technical document mentions neither. It instead shows a parabolic rate curve with an inversion point at 26 ±2°C and specifies adjustment near the 28°C temperature of a worn watch. The document may predate a later revision, but it does not support the usual thermistor claim.

Rolex specified accuracy within one minute per year under normal wear and battery life beyond 24 months. The movement draws no more than 9 microamps, of which the electronics use at most 3. There is no battery end-of-life indication; erratic running is the warning. Hacking cuts current to the motor, and the seconds hand restarts one second after the crown returns to its running position.

The electronic module and motor are sensitive to contamination, and the mobile-frame pivots run dry. Rolex supplied the motor only as a complete unit rather than as separate components.

Cal. 5055

Cal. 5055, engraved "5055," "11 ELEVEN JEWELS," EmmyWatch
detail value
type Quartz
jewels 11
frequency 32,768 Hz crystal
drive Mobile-frame step-by-step motor, pallet fork, 1 beat/s
circuit C-MOS module: oscillator, binary divider, impulse amplifier
rate adjustment Trimmer, about 2 s/d total range
battery 1.55V silver-oxide, 24+ months
size 29.75mm diameter (29.00mm case-fitting), 7.11mm high

Cal. 5055 is the Day-Date counterpart to Cal. 5035. The two share their motor and electronic module, while the 5055's calendar follows the principle of the mechanical Cal. 3055. Its day-disc stack increases the height from 6.35 to 7.11mm.

Cal. 5055 was COSC-certified from its 1977 launch. Cal. 5035 gained certification around 1978–80, alongside a change to a tuning-fork-shaped quartz crystal, so early Oysterquartz Datejust dials lack the "Superlative Chronometer Officially Certified" text found on contemporary Day-Dates.

Cal. 5055 adds the day mechanism and its stricter tolerances. Rolex specified hour-wheel endshake below 0.03mm and calendar change within two minutes of midnight. The day disc is a separate replaceable part, allowing the display language to be changed without altering the movement.

Cal. 5055 powers the yellow-gold ref. 19018, white-gold ref. 19019 and pyramid-bezel ref. 19028. Planned successors, Cals. 5235/5255 with a conventional stepper motor and 5335/5355 with a perpetual calendar, were cancelled before production.

Related but not Rolex

Two commonly confused descriptions are not Rolex calibers. Gruen's Cal. 877, used in the Techni-Quadron, is an Aegler-built architectural sibling of Cal. 300 sold under Gruen's name in the United States. It was never a Rolex commercial number. A Bubbleback-era "9¾ ligne" description records only the movement's size class, not a distinct caliber designation.

Sources

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