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Main Page -> Movements

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Prince (shaped): 300 · 7½ T.S. 300 · 310 · 360 HW · 350 T.S.

Bubbleback / early automatic: 520 · 620 · 600 · A260 · A296 · 645 · 740 · 745

Oyster / Oysterdate Precision: 1210 · 1215 · 1220 · 1225

Vintage sport (1950s–80s): 1030 · 1035 · 1530 · 1560 · 1570 · 1575

Modern sport (1988–2020): 3035 · 3130 · 3135 · 3185 · 3186 · 3187

Milgauss: 1580 · 3131

Daytona chronograph: 72 · 727 · 4030 · 4130

Day-Date: 1055 · 1555 · 1566 · 3055 · 3155

Oysterquartz: 5035 · 5055

Rolex movements

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

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

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

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

Prince (shaped movements)

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

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

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

Cal. 300

detail	value
type	Manual
jewels	15 (Prima) · 18 (Extra/Ultra Prima)
frequency	18,000 vph (2.5 Hz)
power reserve	~50h
size	7½ × 14½ lignes / 16.9 × 32.7mm
escapement	Lateral lever
shock	None

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

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

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

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

Cal. 7½′′′ T.S. 300

detail	value
type	Manual
frequency	18,000 vph (2.5 Hz)
power reserve	~50h
size	7½′′′ rectangular
escapement	Lateral lever
balance	Monometallic
regulator	Micrometer

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

Cal. 310

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

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

Cal. 360 HW

detail	value
type	Manual
jewels	15–18

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

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

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

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

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

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

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

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

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

Cal. 1759

detail	value
type	Manual
jewels	18

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

Cal. 350 T.S.

detail	value
type	Manual
jewels	15 or 18 (documented both ways)
size	16.9 × 32.7mm (T.S.)
escapement	Lateral lever
balance	Monometallic

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

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

Bubbleback and early automatic

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

Cal. 520

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

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

Cal. 620

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

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

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

Cal. 630

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

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

Cal. 10½ Hunter

detail	value
type	Manual
jewels	17–18
frequency	18,000 vph (2.5 Hz)
size	10½ lignes
escapement	Straight-line lever
balance	Superbalance, 6-position
regulator	Swan-neck micrometer

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

Cal. 600

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

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

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

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

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

Cal. A260

detail	value
type	Automatic
jewels	19
frequency	18,000 vph (2.5 Hz)
power reserve	36h
size	26.4mm
escapement	Straight-line lever
balance	Superbalance, blued Breguet spring
shock	Present (unnamed brand)

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

Cal. A296

detail	value
type	Automatic
jewels	18
frequency	18,000 vph (2.5 Hz)
power reserve	36h
size	29.5mm
escapement	Straight-line lever
balance	Monometallic Superbalance
regulator	Index
shock	Shock absorber (775-labelled lots only)

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

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

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

Cal. 645

detail	value
type	Automatic
jewels	17–20
frequency	18,000 vph (2.5 Hz)
power reserve	41h
size	26.4mm
escapement	Straight-line lever
balance	Superbalance, timed to 6 positions
regulator	Index
shock	Shock absorber

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

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

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

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

Cal. 740

detail	value
type	Automatic
jewels	18 base plate (26 in Antiquorum lots — see note)
frequency	18,000 vph (2.5 Hz)
power reserve	Not recorded
size	29.5mm
escapement	Straight-line lever
balance	Superbalance, adjusted to 6 positions
regulator	Index (A.295-labelled lots)
shock	Not named in 740 lot text

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

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

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

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

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

Cal. 745

detail	value
type	Automatic
jewels	18 + 7 rotor
frequency	18,000 vph (2.5 Hz)
power reserve	42h
size	29.5mm
escapement	Straight-line lever
balance	Superbalance
regulator	Index
shock	Shock absorber

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

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

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

Oyster and Oysterdate Precision

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

Cal. 1210

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

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

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

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

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

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

Cal. 1215

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

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

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

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

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

Cal. 1216

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

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

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

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

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

Cal. 1220

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

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

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

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

Cal. 1225

detail	value
type	Manual
jewels	17
frequency	21,600 vph (3 Hz)
power reserve	~58h
size	10½′′′ / Ø23.80mm × 5.07mm height
escapement	Straight-line lever
balance	Screwless, inertia blocks, flat hairspring
regulator	Index with movable stud support
shock	KIF
date	Non-quickset, dragging change

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

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

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

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

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

Cal. 1200

detail	value
type	Manual
jewels	17
frequency	18,000 vph (2.5 Hz)
power reserve	~58h
size	10½′′′ / Ø23.80mm × 3.65mm height
escapement	Straight-line lever, jewelled pallet fork and staff
balance	Glucydur, Breguet overcoil
regulator	Index with movable stud support
shock	"Rolex Shockresisting" device

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

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

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

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

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

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

Cal. 1030

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

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

Cal. 1035

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

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

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

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

Cal. 1530

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

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

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

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

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

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

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

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

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

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

Cal. 1520

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

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

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

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

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

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

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

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

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

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

Cal. 1535

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

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

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

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

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

Cal. 1525

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

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

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

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

Cal. 1560

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

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

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

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

Cal. 1565

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

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

Cal. 1570

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

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

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

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

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

Cal. 1575

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

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

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

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

GMT-Master line

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

Cal. 1036

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

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

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

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

Cal. 1065

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

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

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

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

Cal. 1066

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

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

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

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

Cal. 3075

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

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

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

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

Cal. 3085

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

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

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

Cal. 3175

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

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

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

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

Cal. 3185

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

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

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

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

Cal. 3186

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

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

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

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

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

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

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

Cal. 3187

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

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

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

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

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

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

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

Modern sport calibers (1988–2020)

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

Cal. 3000

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

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

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

Cal. 3035

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

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

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

Cal. 3130

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

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

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

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

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

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

Cal. 3132

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

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

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

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

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

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

Cal. 3135

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

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

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

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

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

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

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

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

Milgauss

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

Cal. 1580

detail	value
type	Automatic
jewels	26
frequency	19,800 vph (2.8 Hz)
power reserve	48h
size	28.5mm × 5.75mm
escapement	Straight-line lever
balance	Free-sprung monometallic, Microstella screws
regulator	None — free-sprung
shock	Shock absorber

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

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

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

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

Cal. 3131

detail	value
type	Automatic
jewels	31
frequency	28,800 vph (4 Hz)
power reserve	48h
size	28.5mm
escapement	Nickel-phosphorus escape wheel & pallet fork
balance	Free-sprung monometallic, Microstella
shock	KIF

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

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

Daytona chronograph (manual-wind)

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

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

Cal. 72

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

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

Cal. 72A

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

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

Cal. 72B

detail	value
type	Manual
jewels	17
frequency	18,000 vph (2.5 Hz)
power reserve	48h
escapement	Swiss lever
balance	Microstella, adjustable inertia
shock	KIF (often Flector)

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

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

Cal. 722

detail	value
type	Manual
jewels	17
frequency	18,000 vph (2.5 Hz)
power reserve	48h
escapement	Swiss lever
balance	Microstella, adjustable inertia
shock	KIF (often Flector)

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

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

Cal. 722-1

detail	value
type	Manual
jewels	17
frequency	18,000 vph (2.5 Hz)
power reserve	48h
balance	Microstella (inherited from 722)
shock	KIF

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

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

Cal. 727

detail	value
type	Manual
jewels	17
frequency	21,600 vph (3 Hz)
power reserve	48h
escapement	Swiss lever
balance	Microstella, adjustable inertia
shock	KIF

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

Daytona chronograph (automatic)

Cal. 4030

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

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

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

Cal. 4130

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

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

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

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

Day-Date

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

Cal. 1055

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

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

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

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

Cal. 1555

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

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

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

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

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

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

Cal. 1556

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

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

Cal. 1566

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

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

Cal. 3055

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

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

Cal. 3155

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

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

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

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

Cal. 3156

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

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

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

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

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

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

Oysterquartz

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

Cal. 5035

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

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

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

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

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

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

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

Cal. 5055

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

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

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

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

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

Related but not Rolex

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

Sources

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