Rolex Caliber & Movement Reference

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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 pages carry the full case-by-case 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.

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.

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.

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.

Movement grading across the family runs Prima → Extra Prima → 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.

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, 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.

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.

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. Whether these track distinct Aegler grading tiers or are simply how UK cataloguers transcribe the grade and jewel count stamped on a given movement is unresolved in the record — 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.

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 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 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).

Cal. 310

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

The centre-seconds member of the T.S. family, built for the wedge-shaped 3361 Aerodynamic / 3362 / 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. 360 HW

Cal. 360 HW, marked "Rolex, 15 Rubies, Swiss Made"

detail	value
type	Manual
jewels	15–18

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 collector-book author Charles Jarman describes Cal. 360 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. 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.

Cal. 510

detail	value
type	Manual
jewels	17

Documented on the Prince Brancard ref. 1855, catalogued as a "17-jewel Cal.510 manual wind movement tested to 8 positions" — the same unusual 8-position adjustment seen on Cal. 1004 below, against the more typical 6-position Prima/Extra Prima/Ultra Prima standard.

Cal. 579

detail	value
type	Manual
jewels	17

Bonhams London catalogued a stainless steel ref. 1862, circa 1935, case No. 103, directly as a "17-jewel Cal.579 manual wind movement" — single-sourced to that one lot. Earlier listings of this number carried a trailing "T," which does not appear in Bonhams' own description; the letter is an aggregator-database artifact rather than Rolex or Aegler terminology, and is dropped here.

Cal. 701

detail	value
type	Manual

The weakest of the numbers on this page: a UK dealer's photograph shows "ROLEX PRINCE 701" legible on a 1930s piece, but no accompanying jewel count, adjustment count, or any other technical description has surfaced anywhere. The marking is real; nothing beyond it is currently documented.

Cal. 841

detail	value
type	Manual
jewels	17 (Bonhams) / 15 (one auction listing)

Bonhams London, ref. 1862 circa 1930, case No. 10403: "17-jewel Cal.841 manual wind." The same number resold through Tajan in 2019 as "17-jewel Cal.841 manual wind" on the identical watch — one example catalogued twice, not two independent sightings. A separate, smaller consignor listing gives 15 jewels for a "Cal. 841T" on a different 1862, a contradiction worth keeping rather than resolving. As with Cal. 579, the trailing "T" seen in some listings traces to an aggregator database field, not the original auction-house text.

Cal. 1004

detail	value
type	Manual
jewels	17

Bonhams London, 18K two-colour gold bracelet ref. 1862, Glasgow import mark 1936: "17-jewel Cal.1004 manual wind movement tested to 8 positions" — the same 8-position outlier seen on Cal. 510, against the usual 6-position standard.

Cal. 1130

detail	value
type	Manual
jewels	16

Documented on a 9K yellow gold ref. 1490, case 30280, catalogued as a "cal. 1130 manual winding lever movement, 16 jewels" — the lowest jewel count recorded for a numbered Prince movement on this page.

Cal. 1439

detail	value
type	Manual
jewels	18

Bonhams, Prince Chronometre ref. 1490, Glasgow import mark 1937: "18-jewel Cal.1439 manual wind movement timed to 6 positions" — back to the standard 6-position count after the 510/1004 outliers.

Cal. 1759

Cal. 1759, "1759, 18 RUBIES, ULTRA PRIMA," with its matching case back

detail	value
type	Manual
jewels	18

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.

Cal. 350 T.S.

detail	value
type	Manual
jewels	18
size	16.9 × 32.7mm (T.S.)
escapement	Lateral lever
balance	Monometallic

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 1491 Brancard Jumping Hour: an 18-jewel, chronometer-rated movement on the T.S. base, in the 1491's rectangular case. 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.

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.

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.

Cal. 520

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

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 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. 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)

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.

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 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.

Cal. 10½ Hunter

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

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.

Cal. 600

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

A 9¾-ligne manual caliber, one size class below the 10½-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 — 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."

Rolex's factory caliber table lists Cal. 600 as a Basic Caliber rather than a derivative — 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 9¾-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.

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.

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.

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)

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.

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)

1952–55, 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 — 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 — 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 — Phillips' Geneva Watch Auction FOUR framed the A296-to-1030 swap explicitly as a thickness change, not a different winding concept.

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 — a balance adjusted to 6 positions and a shock absorber — 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 — a size code covering two commercial numbers, which is what a size code is supposed to do.

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'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.

Cal. 645

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

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.

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 & 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 — 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 — 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.

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 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.

Cal. 740

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

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 — the slightly earlier sibling of the A.296 group above.

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 10½ 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.

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 — Bonhams itemises the sister 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.

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 — 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.

Cal. 745

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

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 — 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.

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 — 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.

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 — 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.

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 Rolex's manual-wind era entirely — the Oysterdate Precision 6694 is documented as the last manual-wind Rolex ever put into production, outlasting even the hand-wound Daytona by a year. Six commercial numbers cover the family, distinguished by seconds placement, date, and beat rate rather than separate architectures.

Cal. 1210

detail	value
type	Manual
frequency	18,000 vph (2.5 Hz)
power reserve	~58h
size	4.27mm height

The base caliber of the family: center (sweep) seconds, Breguet hairspring. Powers the Oyster Precision 6426 and an early Crott-catalogued example in ref. 6082. Fratello and Horbiter disagree on whether Cal. 1200 or Cal. 1210 is the true architectural base of the group; the point is unresolved between them.

Cal. 1215

detail	value
type	Manual
frequency	18,000 vph (2.5 Hz)
size	5.07mm height

Cal. 1210 with a date module added, the extra mechanism accounting for the jump from 4.27mm to 5.07mm in height. Powers the Oysterdate Precision 6694 in its early production and the earlier 6094/6294/6494 Oysterdate references. Non-quickset — the date advances only by running the hands through midnight.

Cal. 1216

detail	value
type	Manual
jewels	17

A 17-jewel variant of Cal. 1215, otherwise architecturally identical.

Cal. 1220

detail	value
type	Manual
frequency	21,600 vph (one source gives 19,800 — see note)

The Cal. 1210 platform without the Breguet overcoil, run at a raised beat rate. Horbiter, Fratello, and Chrono24 all give 21,600 vph; one specialist catalogue gives 19,800 vph for the same caliber, an unresolved discrepancy. Powers later-production Oyster Precision 6426.

Cal. 1225

detail	value
type	Manual
power reserve	~58h
size	4.27 → 5.07mm height
shock	KIF

Cal. 1220 with a date module added, carrying later-production Oysterdate Precision 6694 through the family's final years. None of the six Precision calibers on this page were chronometer-certified, which is why "Precision" rather than "Superlative Chronometer" appears on the dial across the whole line.

Cal. 1200

detail	value
type	Manual
size	3.65mm height

The small-seconds variant of the family, thinner than the sweep-seconds Cal. 1210 it's otherwise architecturally close to.

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.

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

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.

Cal. 1035

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

The date version of Cal. 1030, from 1957, powering the Oyster Perpetual Date 6518, 6530, and 6534 and the Datejust Thunderbird 6609. Non-quickset — 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.

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 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" — 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.

Cal. 1530

Cal. 1530-era butterfly rotor halves, Rolex coronet stamped

detail	value
type	Automatic
jewels	17→25→26
frequency	18,000 vph (2.5 Hz)
power reserve	44h
escapement	Swiss lever
balance	Screwed Glucydur

1957–65, 17 jewels early rising to 25 then 26 late, 18,000 vph, 44 hours. Traditional Swiss lever escapement with a 15-tooth club-tooth wheel, screwed Glucydur balance. The rotor shape evolves mid-production from butterfly to half-moon, and later runs add blued screws on the auto-winding bridge with red Teflon-coated gears replacing brass — both genuine dating markers for a given example. First Submariner appearance is the 5510 in 1958–59, not yet chronometer-rated; chronometer certification arrives with Cal. 1560 on the 5512 instead. It also powers the 36mm Explorer-case 5504 Air-King alongside the early 5500 production, and Bonhams has catalogued it in a 1002 and a 1003 against the Watch-Wiki concordance that assigns it to the 5500 family only — a documented outlier, not a confirmed cross-reference pattern. Cal. 1530 was deliberately never COSC-certified across most of its run: regulating a labor-intensive screwed balance to chronometer tolerance at Rolex's production volume was judged uneconomical, a cost decision rather than a technical shortfall.

Cal. 1520

Cal. 1520, engraved "1520," EmmyWatch

detail	value
type	Automatic
jewels	17 / 25 / 26
frequency	19,800 vph (2.8 Hz)
balance	Monometallic, flat hairspring
regulator	Index

The permanent non-chronometer twin of Cal. 1530, 1963–90, 17/25/26 jewels at 19,800 vph — the 17-jewel variant is a US/Canada import-duty-bracket move, not a different movement. Monometallic balance, index regulator, and a flat (non-Breguet) hairspring — the cost reduction that keeps it out of chronometer certification, confirmed across seven independent Antiquorum lot descriptions against occasional secondary sources that wrongly credit it with a Breguet overcoil. It powers late 5513, 5514, and 5517 Submariners and the long-running 5500 Air-King from 1963 onward, plus the 1002 Oyster Perpetual, 5501, and 5520.

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

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.

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.

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.

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.

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

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.

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.

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.

Cal. 1560

Cal. 1560, EmmyWatch

detail	value
type	Automatic
jewels	26
frequency	18,000 vph (2.5 Hz)
power reserve	42h
escapement	Swiss lever
balance	Free-sprung, Microstella
shock	KIF Flector

1959–65, 26 jewels, 18,000 vph, 42 hours, the cross-family chronometer bridging Cal. 1530 and Cal. 1570 architecturally. It gains jewels over the 1530 and, like the 1570 after it, carries COSC certification, without yet reaching the 1570's higher 19,800 vph beat rate. The balance assembly is Rolex part number 7980: Microstella regulation screws, a free-sprung Breguet overcoil hairspring, and KIF Flector shock protection, the same balance package the 1570 inherits unchanged. Powers mid-production 5512, 1675, and 1016.

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

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.

Cal. 1570

Cal. 1570, open caseback

detail	value
type	Automatic
jewels	26
frequency	19,800 vph (2.8 Hz)
power reserve	44h
size	28.5mm × 5.75mm
escapement	Swiss lever
balance	Free-sprung, 2 Microstella screws
shock	Kif Ultraflex

1965–80, 26 jewels, 19,800 vph, 44 hours, 28.5 × 5.75mm — the higher-beat successor to Cal. 1560, with hacking added mid-life. Free-sprung Breguet hairspring with screw-based poising, two Microstella screws for regulation, Kif Ultraflex shock protection. It runs across the Submariner and Explorer lines through the late 1970s, and dealer listings that describe a "1500" as carrying Cal. 1575 are often describing a 1570 instead — the movement resolves the confusion, not the dial text.

Cal. 1575

Cal. 1575, EmmyWatch

detail	value
type	Automatic
jewels	25
frequency	19,800 vph (2.8 Hz)
power reserve	50h
balance	Free-sprung (inherits 1570 balance)
shock	Kif Ultraflex

1965–80, 25 jewels, 19,800 vph, 50 hours — adds either a date module or a GMT module onto the 1570 base, which is how the same caliber number lands on the 1680 (date), the late 1675 (GMT), and the 1655 Explorer II (GMT with 24-hour bezel) simultaneously.

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.

Cal. 1036

Cal. 1036, EmmyWatch

detail	value
type	Automatic
jewels	25
frequency	18,000 vph (2.5 Hz)
power reserve	42h
escapement	Straight-line lever (inferred, 1030 base)
shock	KIF (inferred)

1954–59, 25 jewels, 18,000 vph, 42 hours — the first GMT caliber, in the bakelite-bezel 6542. Rotor and bridge spell out "TWENTY FIVE JEWELS" in full rather than abbreviating it, an early-production engraving convention that helps date a given example.

Cal. 1065

Cal. 1065, EmmyWatch

detail	value
type	Automatic
jewels	25
frequency	18,000 vph (2.5 Hz)
power reserve	42h
escapement	Straight-line lever (inferred, 1030 base)
shock	KIF (inferred)

1956–59, 25 jewels, 18,000 vph, 42 hours, the mid-6542 GMT caliber succeeding Cal. 1036 within the same bakelite-bezel generation.

Cal. 1066

detail	value
type	Automatic
jewels	25
frequency	18,000 vph (2.5 Hz)
power reserve	42h

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. All three 6542 calibers (1036, 1065, 1066) share the base 1030 architecture with a GMT module added — same straight-line lever escapement, monometallic balance, blued Breguet spring, index regulator, KIF shock protection, confirmed directly for the 1066 across three separate Antiquorum lots using word-for-word the 1030 formula; the inheritance for 1036 and 1065 specifically is not independently attested and should be read as inferred rather than observed. The GMT module adds roughly 0.18mm of height over the plain 1030 and changes nothing in the regulating organ. 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.

Cal. 3075

Cal. 3075, engraved "3075," EmmyWatch

detail	value
type	Automatic
jewels	27
frequency	28,800 vph (4 Hz)
power reserve	48h
escapement	Swiss lever
balance	Free-sprung, four Microstella screws
shock	KIF

1979–88, 27 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer — carries the synchronized "caller" GMT layout into the 16750/16753/16758 generation. Free-sprung balance with four gold Microstella screws on the inner rim, Breguet overcoil, Swiss lever escapement, KIF shock protection at both balance jewel stations — the same regulating organ as Cal. 3035, carried on a balance cock rather than a bridge.

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 (inferred)

1983–89, 27 jewels, 28,800 vph, 48 hours, hacking, chronometer. The first Rolex caliber to dissociate the local-hour hand from the 24-hour hand: with the crown in its second (one-click-out) position, turning it jumps the local hour hand forward or backward in full one-hour steps — snapping cleanly to each hour rather than sweeping through the minutes — while the minute and seconds hands, and the 24-hour "home time" hand, stay completely undisturbed. A traveler resets local time without touching the hand tracking home. The cost is quickset date, which now advances only via the local-hour hand. The 6.3mm figure widely quoted for its case-driving thickness is contradicted by Rolex's own parts diagram, which gives 7.20mm — either way the movement's thickness drove the 16760 "Fat Lady" / "Sophia Loren" case proportions, and it ran exclusively in the 16760 GMT-Master II and the 16550 Explorer II.

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 × 6.0mm
escapement	Swiss lever
balance	Monometallic Glucydur, free-sprung
regulator	Microstella screws, no index
shock	KIF Elastor

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 — architecturally it's a date-less Cal. 3135, sharing that caliber's finishing standard rather than being a modest refresh of the simplified 3000.

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 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.

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.

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.

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

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.

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 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.

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.

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 −4/+6 seconds a day on the bare movement to −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.

Cal. 3175

Cal. 3175, EmmyWatch

detail	value
type	Automatic
jewels	31
frequency	28,800 vph (4 Hz)
power reserve	48h

1988–99, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer, adjusted to 5 positions and temperature, Glucydur balance with Microstella, Breguet hairspring, Kif shock. The last "caller" GMT and the last fixed-GMT caliber Rolex built, running in a single reference, the 16700 — the 24-hour hand stays linked to local hour, and the second time zone reads off the bezel rather than an independent hand, keeping the older synchronized layout alive right up to 1999 even as the rest of the GMT line had already moved on to the jumping-hour Cal. 3185.

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, two Microstella nuts

1989–c.2007, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer, KIF Elastor shock. Derived directly from the Cal. 3135 platform with an added 24-hour GMT hand mechanism, powering the 16710, 16713, 16718, and 16570. Both Microstella nuts are always adjusted identically as a pair, a documented service note to avoid poise imbalance. At 6.45mm it's noticeably slimmer than the 7.2mm Cal. 3085 it replaced, part of why the 16710 case reads thinner on the wrist than the earlier "Fat Lady" 16760.

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

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.

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.

Underneath the GMT work the movement is Cal. 3135 architecture: the 3185 that preceded it was built on that framework with a 24-hour hand and its own train added, 28.5mm across and 6.45mm tall, and the 3186 keeps the 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.

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.

The break from the 3185 is not only the hairspring. The 3185 advanced its date from a simple ratchet acting on the hour wheel; the 3186 substitutes a jumping-hour click spring and moves the drive-train wheels closer together, taking the slack out of the independently-set hour 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.

Cal. 3187

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

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 −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.

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.

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.

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.

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.

The −2/+2 figure needs a date attached to it. Rolex redefined Superlative Chronometer in 2015, taking the guaranteed rate from COSC's −4/+6 seconds a day on the bare movement to −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.

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 counterpart introduced the same year as Cal. 3000, becomes the single dominant modern Rolex workhorse across 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
size	28.5mm × 5.8mm
balance	Adjustable-mass, flat hairspring

1989–99, 27 jewels, 28,800 vph, 42 hours (some owners report 45–60 hours in practice), 28.5 × 5.8mm — the first 28,800 vph time-only movement of the modern era, based on Cal. 3035 and powering the 14000 Air-King, 14010, 14060 Submariner, and 14270 Explorer. Deliberately simplified against the outgoing 1570 generation: a flat hairspring with no Breguet overcoil, and an adjustable-mass balance with no separate regulator arm at all. The automatic-winding module runs oversized components, including PTFE-coated red-alloy click wheels, and watchmakers commonly single out the winding module as the best-finished part of an otherwise deliberately economical movement.

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

1977–88, 27 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer — the first quickset Submariner caliber, in the 16800, 168000, 16808, and 16803. Free-sprung balance, four Microstella regulating screws, Breguet overcoil in Nivarox alloy, KIF Elastor shock protection, held on a cantilever balance cock rather than the full bridge Cal. 3135 introduces later — the hairspring is glued to the balance-cock stud here, where the 3135 switches to a laser-welded attachment. Quickset works by giving the crown an intermediate position that connects directly to the date wheel, bypassing the hour wheel entirely — on a non-quickset movement the only way to advance the date is to run the hands forward through midnight, sometimes dozens of times to skip a long month. The date wheel gear path runs differently through the movement than on a non-quickset caliber, which is why the feature can't be retrofitted after the fact.

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
balance	Free-sprung, four Microstella nuts

1988–2018, 31 jewels, 28,800 vph, 48 hours, hacking, quickset, chronometer — Rolex's 30-year workhorse, running the 16610, 16613, and 16618 through to the 116610 generation. Rhodium-plated finish, beveled and polished chamfered screws, a two-piece axle-style bidirectional rotor, and four Microstella nuts for regulation that need a dedicated Microstella key. The reversing wheels (Rolex part 32135-540) are anodized purple-red and visible straight through the rotor cutout — an easy, no-disassembly identification marker. The hairspring material switched from Nivarox to Parachrom Blue circa 2007–2008, a running production change collectors use to help date an individual movement without opening the case.

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.

Cal. 1580

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

Powers the Milgauss 1019 exclusively across its entire 1960–1988 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.

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 — 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.

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 — 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.

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 — 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.

Cal. 3131

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	Paramagnetic blue Parachrom
shock	KIF

A date-less Cal. 3130 derivative built for the Milgauss 116400 and 116400GV "Glace Verte" (2007–2023), and the Air-King 40 ref. 116900 (2016–2022). Anti-magnetism runs three layers deep rather than one: a two-part soft-iron shield around the movement — its interior engraved with a "B" and arrow, the symbol for magnetic flux density, visible only to Rolex-trained watchmakers — a paramagnetic blue Parachrom hairspring, and an escape wheel and pallet fork machined in amorphous nickel-phosphorus rather than steel, the detail most write-ups skip. COSC-certified for its entire run, the 3131 never received the Chronergy escapement or the tightened −2/+2 Superlative rating that later reached the rest of the sport line — the Milgauss was discontinued before that upgrade cycle arrived.

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 — it built the unfinished movement blank, not a complete Rolex-designed caliber — 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.

Cal. 72

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

1960–65, 17 jewels, 18,000 vph, 48 hours — a bare Valjoux 72 with minimal Rolex finishing, in the 6234 and earliest 6238. Rolex left the stock Valjoux regulating organ untouched at this stage: index regulator, flat hairspring, factory Incabloc shock protection — the standard configuration off any Valjoux 72 ébauche, not yet a Rolex-specific balance package.

Cal. 72A

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

Early-to-mid 1960s, 17 jewels, 18,000 vph, 48 hours — a Rolex-finished intermediate step between Cal. 72 and 72B; thinly documented in the collector record. It keeps the same stock regulating organ as Cal. 72: index regulator, flat hairspring, Incabloc shock — the finishing changed, the internals did not yet.

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)

1962–65, 17 jewels, 18,000 vph, 48 hours: the final pre-722 Valjoux 72 execution, in the early 6238. This is where Rolex actually intervenes in the movement rather than just finishing it: the stock index regulator and flat hairspring are replaced with a Microstella adjustable-inertia balance and a Breguet overcoil, regulating by inertia rather than a curb-pin index, and the shock system switches to KIF, often the clover-shaped Flector variant. Watch historian Pucci Papaleo, who has serviced large numbers of these movements, states there is no substantial mechanical difference between the 72B and the 722 that follows it — the regulating-organ swap described here is what actually separates 72B from 72A, not the 72B-to-722 rename. The name change reflects Rolex re-branding the same finished movement for its own advertising and parts catalogues, not a new architecture.

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)

1963–69, 17 jewels, 18,000 vph, 48 hours — the first Rolex-stamped Valjoux 72, powering the original 6239 alongside the 6240 and 6241 generation, the run that includes the "Paul Newman" dial variants. Rolex used "72B" and "722" interchangeably on its own technical documentation for the same regulating package — Microstella balance, Breguet overcoil, KIF shock, column-wheel chronograph with yoke coupling.

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

1969–70, 17 jewels, 18,000 vph, 48 hours — a transitional revision of Cal. 722 bridging into the higher-beat Cal. 727 era. Unlike the largely cosmetic 72B-to-722 rename, this one is a genuine mechanical change: Rolex altered the shape of the hour-recorder conveyor in the chronograph coupling mechanism so it engaged more smoothly with its driving wheel, the fix that let the higher-beat 727 run reliably at 21,600 vph shortly after. It also adds a hairspring guard spring, a metal sheet stopping the hairspring sliding over its stud support under impact — introduced here but not consistently fitted, so many surviving movements 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

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.

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

1988–2000, 31 jewels, 28,800 vph, 54 hours, chronometer — Rolex's most disputed movement specification, and the last foreign-sourced caliber in its modern line. The working outline is a heavily reworked Zenith El Primero base, launched with the 16520 for a twelve-year run; serious sources agree on the 28,800 vph rate, a free-sprung Breguet balance, and no date function, but diverge on the exact length of Rolex's modification list and quote the power reserve as either 52 or 54 hours depending on source. The photographed example, marked "MONTRES ROLEX S.A. GENEVA SWISS, ADJ. 5 POSITIONS TEMPERATURE, THIRTY-ONE JEWELS" with "4030" in a small stamped box, is a clean confirmation of the caliber regardless of which modification-list version a given source favors.

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

2000–2023, 44 jewels, 28,800 vph, 72 hours, chronometer: Rolex's first fully in-house chronograph movement, launched with the 116520. Column-wheel construction with a vertical clutch, 201 components, and the first Rolex chronograph to run on a ceramic ball-bearing rotor (7 balls on 3 screws) rather than a sleeve bearing, cutting the part count below the Cal. 4030 it replaced despite the added complexity. A conventional Swiss lever escapement, not the Chronergy escapement that arrives only with the 4131 successor — the free-sprung balance is held by a transversal bridge screwed at both ends rather than a cock, the bridge's own rigidity doubling as a shock-resistance measure, backed by KIF shock protection rather than the later Paraflex system. Solid caseback only; the display back doesn't arrive until the 4131 successor in 2023 either. The vented rotor carries a proprietary Rolex striping pattern, a visual tell against generic aftermarket rotors sometimes swapped into grey-market builds. Parachrom hairspring from launch, though sources disagree on when the blue oxide-coated version specifically arrived — readings range from 2005 to "all Daytona movements since 2007," not fully reconciled. It powered the whole pre-ceramic in-house Daytona generation and carried forward into the 116500LN.

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.

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

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. Straight-line Swiss lever escapement, KIF shock protection, monometallic balance adjusted to temperature and five positions, self-compensating Breguet balance spring. Rhodium-plated, with oeil-de-perdrix ("partridge-eye") circular graining on the finish rather than Côtes de Genève stripes. The generation-1 movement (6510/6511) pre-dates COSC certification; the generation-2, engraved "1055B" on the bridge rather than "1055," adds full COSC rating and carries "Superlative Chronometer Officially Certified" on the dial in place of the earlier "Officially Certified Chronometer" script. Sources disagree on whether the free-sprung Microstella balance is a 1055B-only upgrade or already present on the base 1055 — both readings appear in the record, unresolved. No quickset, no hacking, on either generation.

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

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.

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 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.

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.

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.

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

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). 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; examples built before that date do not hack, a genuine running change rather than a running fault.

Cal. 1566

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

The only caliber Rolex built for a single specific case: the platinum 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. 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

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. 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

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: turn clockwise to advance the date, counterclockwise to advance the day. Cal. 3055 could only do half of that. The 27-to-31 jewel jump over the 3055 traces to a real architectural change, not just the added quickset: a full transversal balance bridge replaces the 3055's balance cock, paired with a larger balance wheel. Free-sprung Glucydur balance with Microstella, Nivarox Breguet overcoil moving to Parachrom from around 2008-10, KIF Elastor shock protection — this caliber never received the later Paraflex system. The hairspring stud attachment also changes here, from glued (3035/3055) to laser-welded. Height is commonly quoted at 6.00mm; Rolex's own parts document gives 6.45mm. The double-quickset the 18238 introduced carried the 6-digit 118238 family for three decades on the same movement.

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

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

Sources

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• Hodinkee — A Vintage Watch Nerd's Critical Dissection of the Rolex Daytona, Part 1 (Paul Boutros, 2012)
• Hodinkee — A Vintage Watch Nerd's Critical Dissection of the Rolex Daytona, Part 2 (Paul Boutros, 2013)
• Monochrome — In-Depth: The History of the Rolex Daytona (Erik Slaven, 2024)
• Monochrome — History of the Rolex Submariner, Part 1 (Tom Mulraney, 2020)
• Monochrome — History of the Rolex Submariner, Part 2 (Tom Mulraney, 2020)
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• A Collected Man — Is the Rolex Pre-Daytona a Forgotten Classic? (Russell Sheldrake, 2020)
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• Sotheby's — Submariner Ref. 6538, Stainless Steel With 4-Line Tropical Dial, Circa 1958
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• Sotheby's — auction lot catalogue
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• The Vintage Rolex Field Manual — Colin A. White, Morning Tundra