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Rolex 5100 Beta 21

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Beta 21 → 5100

Rolex Beta 21 ref. 5100 in white gold, front view, on its integrated bracelet
Rolex Beta 21 ref. 5100 in 18K white gold, Phillips Hong Kong.

Rolex launched Ref. 5100 on 5 June 1970 as its first quartz wristwatch. The watch used the 13-jewel, 8kHz Beta 21 module developed by the Centre Electronique Horloger (CEH), a consortium of about twenty Swiss watch houses that included Omega, Patek Philippe, and Piaget. Rolex designed the 5100's case, dial, and integrated bracelet around that shared movement; the movement itself was a consortium design.

Rolex discontinued the 5100 in 1972 and left the CEH that year. It then developed the proprietary calibers 5035 and 5055 for the Oysterquartz line, introduced in 1977. Auction catalogues also call the 5100 "Texano" or "The Texan"; those names are used in dealer and auction-house catalogues rather than in the Rolex references cited here.

Core facts

detail value
reference 5100
model names Beta 21; also catalogued as "Texano" or "The Texan"
production 1970-1972
case materials 18K yellow gold, 18K white gold
case diameter approximately 39mm across the width (tonneau case; see Case, bezel, crystal, and crown)
case shape tonneau, angular
crystal sapphire, Rolex's first
movement Beta 21 quartz module, cal. RE10, Beta 21; 8kHz, 13 jewels (one lot records 15, see Movement notes)
dial silvered (white gold cases) or gilt/gold-coloured (yellow gold cases); text reads "water resistant," not "waterproof"
bracelet integrated, same metal as the case, concealed deployant clasp

Where it sits in the line

The 5100 was Rolex's contribution to the CEH quartz project. Rolex joined about twenty other Swiss manufacturers instead of developing a movement alone. The resulting Beta 21 powered watches such as Patek Philippe ref. 3587 and the IWC Da Vinci, while each manufacturer designed its own case and dial.

The 5100 differs from Rolex's other watches of the period. It uses a non-Oyster, non-waterproof tonneau case with a screw crown because the Beta 21's dimensions required a different case design. In this model, the movement set the case constraints.

After leaving the CEH in 1972, Rolex developed the proprietary calibers 5035 and 5055 for the Oysterquartz, launched in 1977. The Beta 21 was a shared consortium movement; the Oysterquartz calibers were Rolex designs made for a conventional Oyster case. The 5100 therefore belongs to the Beta 21 project rather than to the later Oysterquartz family.

Production outline

Documented case numbers include 104, 184, 192 (twice), 644, 773, and 794, together with dealer references to numbers above 1,000. Individual watches carry an engraved edition number rather than a conventional Rolex serial. The published sources reviewed here do not establish a confirmed total production figure.

Christie's calls a 1,000-piece run, 900 in yellow gold, 100 in white gold, "believed" rather than confirmed. Hodinkee lays out three separate, mutually exclusive collector theories: something close to 700 yellow gold and 300 white gold; something closer to 900 and 100; or two separate batches of 900 yellow and 100 white apiece, for roughly 2,000 total. None of the three theories is sourced to a Rolex production document, and the published examples include numbers above 1,000. The supported conclusion is narrower: production ran from 1970 to 1972 in yellow and white gold, while the total quantity remains undocumented in the sources reviewed here.

One case number turns up twice in the Phillips record. Case No. 192 sold at The Geneva Watch Auction: NINE in May 2019 for CHF62,500 against a CHF15,000-25,000 estimate, then reappeared at The Geneva Watch Auction: XX in 2024, selling for CHF48,260 against a CHF30,000-60,000 estimate. The matching number and repeated auction description are consistent with one watch being re-consigned, but the records do not prove that.

Movement notes

The Beta 21 was not a Rolex design. The CEH developed it collaboratively, first showing a prototype in 1967. In 1968 the consortium's roughly twenty member houses agreed to produce about 6,000 of the movements, and a few hundred Beta 21 watches appeared at Baselworld in 1969, a year before Rolex's own 5100 reached the market. One source puts the consortium at 21 watchmakers rather than 20; neither figure is resolved against the other here, and both are given with attribution rather than picking a winner. Rolex could make only limited modifications to the shared movement, which is the reason the case exists in the unusual form it does: the electronics came first, and the case had to be built around them.

Rolex and the auction houses catalogue the movement as cal. RE10, Beta 21, 8kHz, 13 jewels, in the descriptions given by Sotheby's, Christie's and Antiquorum. One Phillips lot (The Hong Kong Watch Auction: EIGHT) instead gives 15 jewels for the same designation. Nothing in the sourced record explains the gap, and no second lot corroborates it, so it reads as a catalogue transcription slip rather than a documented second variant.

The Beta 21 uses a sweep centre-seconds hand driven through a pallet wheel. Christie's describes this as a feature of the early Beta 21 generation; later quartz movements commonly used a stepper motor with a one-second jump.

Rolex's own successor movements, cal. 5035 and 5055, share none of this architecture. They are proprietary designs built five years later specifically to fit a standard Oyster case, a different engineering answer to a problem the Beta 21 had already tried to solve.

Dial map

Two documented dial colours track the two case metals: silvered dials on white gold cases, gilt or gold-coloured dials on yellow gold cases. Both carry "ROLEX" and "QUARTZ" printed on the dial, a date aperture at 3 o'clock, and, on at least one yellow gold example catalogued by Antiquorum, a Cyclops lens over the date. The dial text itself carries one detail worth noting for what it does not say: it reads "water resistant," not the "waterproof" language Rolex used across its Oyster-cased catalogue of the same years, a small wording difference that tracks the case's non-Oyster construction rather than a lesser build standard.

Case, bezel, crystal, and crown

Caseback of a Rolex 5100 engraved with the limited-edition number 104
Caseback of case No. 104, engraved with its limited-edition number, Antiquorum Hong Kong.

The case is tonneau-shaped and integrated with the bracelet. Phillips describes its lines as angular and calls the design the first major departure from the Oyster case; the 5100 itself is not an Oyster case. It has a snap-on back and a fluted bezel.

Case diameter is given as approximately 39mm across the width on the majority of sourced lots, four separate Phillips lots and one Antiquorum lot agree on this figure. One Christie's lot gives 40mm, and Antiquorum records one example at 45 x 39mm, measuring both axes of the tonneau shape rather than a single diameter. Taken together, these read as measurement-convention differences on a non-round case rather than evidence of more than one case size.

Every documented case is 18K gold, yellow or white, with no steel examples surfacing across the sourced auction record. White gold examples are consistently described as the scarcer of the two: Phillips catalogue language calls white gold "exceedingly rarer" and states that "no more than a handful" of white gold examples have ever come to auction, while Christie's puts a number on it directly, fewer than 15 differently numbered white gold examples sold at auction in the twenty years before its 2022 lot.

The crystal is synthetic sapphire. Rolex and auction catalogues describe the 5100 as the brand's first watch to use sapphire; sapphire became more common in later Rolex production.

Bracelets, end links, and clasps

Angled view of a white gold Rolex 5100 showing the faceted integrated bracelet
Integrated faceted-link bracelet on a white gold example, Phillips Hong Kong.

The bracelet is integrated with the case rather than a separate fitment, built in the same 18K gold as the case, with a concealed deployant clasp. One Antiquorum-catalogued yellow gold example names its bracelet maker directly: Jean-Pierre Ecoffey of Geneva, a detail not repeated on any of the other sourced lots and not established here as the standard supplier for the line as a whole. Bracelet lengths recorded across the sourced lots run from about 170mm to 200mm, consistent with an adjustable integrated design rather than a fixed single length.

Special branches: the CEH consortium and the Beta 21

The 5100 uses the Beta 21 movement shared by the CEH consortium. The Centre Electronique Horloger began work on a quartz wristwatch caliber in the early 1960s. Sources cited for the project describe a Beta 1 prototype in 1960 and the Beta 21 entering series production in 1969, with a stated accuracy of about five seconds per month.

CEH members used the shared Beta 21 under their own references and case designs. Patek Philippe ref. 3587 and the IWC Da Vinci are documented examples. Rolex's contribution was the angular tonneau case used for the 5100.

By 1972, Rolex had discontinued the 5100 and left the CEH. It then spent five years developing the proprietary Oysterquartz calibers 5035 and 5055, designed to fit a standard Oyster case.

Auction record

Sale Date Metal Case No. Result
Christie's, Geneva May 2017 white gold, new-old-stock 794 estimate CHF100,000-150,000
Christie's, Geneva May 2017 yellow gold n/a estimate CHF15,000-25,000
Sotheby's 2014 white gold, full set n/a sold CHF125,000 (estimate CHF30,000-50,000)
Sotheby's 2013 white gold n/a sold CHF32,500 (estimate CHF15,000-25,000)
Phillips, The Geneva Watch Auction: NINE 12 May 2019 white gold 192 sold CHF62,500 (estimate CHF15,000-25,000)
Phillips, The Geneva Watch Auction: XX 2024 white gold 192 sold CHF48,260 (estimate CHF30,000-60,000)
Phillips, The Hong Kong Watch Auction: FIVE n/a white gold 184 estimate HK$350,000-550,000
Phillips, The Hong Kong Watch Auction: EIGHT n/a yellow gold ("Texano") 644 estimate HK$160,000-250,000
Sotheby's, Important Watches: Part II n/a white gold ("The Texan") 225/87 estimate CHF30,000-50,000
Sotheby's, Watches Weekly, Geneva n/a yellow gold ("The Texan") 315/249 estimate CHF12,000-18,000
Antiquorum, Hong Kong 23 July 2020 yellow gold 104 estimate HKD135,000-230,000
Christie's, New York, Kairos Collection Part III 2022 white gold 773 lot 104

The auction sample is too small and spans several currencies and years to support a price trend. It also mixes full sets with watch-only lots and contains more white-gold records than yellow-gold records. Christie's, Phillips, Sotheby's, and Antiquorum each catalogue the 5100 in the records listed here.

  • Rolex 5100 Beta 21, front view
    Rolex 5100 Beta 21, front view
  • Caseback with engraved edition number
    Caseback with engraved edition number
  • Integrated gold bracelet
    Integrated gold bracelet

Sources


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