Reference:2764

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Bubbleback → 2764

The 2764 is a late-pre-war and early-post-war Bubbleback with three points of interest a collector keeps returning to. The dial sometimes carries the “Super Precision” mark rather than the ordinary “Precision” or “Officially Certified Chronometer” line, a chronometer-grade distinction that Rolex reserved for the tightest-adjusted movements of the period. The movement number itself is the ref 2764’s second oddity: Cal. 620N, with a suffix that collector forums have argued about for years. Is it a technical grade indicator or a parts-catalog sizing code? The parts-catalog reading is the one supported by the evidence. And the reference turns up in retailer variants that are themselves collector categories. Zell Bros of Portland, Oregon sold a configuration they called the “Turtle Perpetual”; Birks in Canada sold two-tone champagne examples with their own retailer signature below the coronet. Three points of interest that cluster on one late-Bubbleback reference.

Core facts

detail value
reference 2764
family Bubbleback
production c.1937–1948
case diameter 31–32mm (measurement method varies)
lug-to-lug approximately 39mm
thickness approximately 13mm
lug width 19mm
case construction two-piece Oyster (bezel + mid-case + screw-down caseback)
bezel smooth, fixed, polished
crystal acrylic
crown screw-down
movement Cal. 620N (9¾ ligne, 18,000 bph, 17j, Breguet overcoil)
power reserve 35–41 hours
dial text “SUPER PRECISION” / “Precision” / “Officially Certified Chronometer”
retailer variants Zell Bros. (Portland, OR) “Turtle Perpetual”; Birks (Canada)
case materials stainless steel (most common at auction), gold shell, gold-plated

Where it sits in the line

The 2764 is a mid-to-late-run member of the second-generation Bubbleback family, the generation that begins with the two-piece case transition of 1936 (refs 3131 and 3132) and continues through the post-war period until the flat-caseback architecture of Cal. 1030 arrives in 1950. The 2764’s earliest documented case is Heritage’s example numbered 107524; the Phillips Geneva Watch Auction THREE lot (case 107118) is dated 1941. The observed serial range, paired with the mature two-piece Oyster case and the 620-family movement, places production in a window roughly 1937 through 1948.

Within that window, the 2764 is a civilian dress Bubbleback in the 31–32mm size bracket, the default Oyster Perpetual case size before the 36mm Ovettone family (4467 and siblings) arrives in 1945 with the first Datejust. The 2764 is a conventional 32mm Bubbleback executed at the precision end of Rolex’s mid-century range, without the date window, Jubilee bracelet, or Big Bubbleback case that define the Datejust.

The measurement variance (31mm on the Phillips and Heritage catalog listings, 32mm on most dealer descriptions) is the same caveat that attaches to every tonneau-cased Bubbleback of the period. Width across the case flanks reads smaller than width including the lug tips. The physical case does not change; the measurement method does.

The “Super Precision” mark

The most distinctive 2764 dials are the ones marked “SUPER PRECISION” below “Oyster Perpetual.” That mark designates a chronometer-grade movement, a Cal. 620 adjusted in multiple positions and passed against the Swiss timing standards of the day, at the higher end of Rolex’s internal precision hierarchy. The standard 620 is a 17-jewel automatic with standard adjustment; the “Super Precision” examples received closer timing work, and the additional dial mark reflected that.

Three dial text configurations appear on surviving 2764 examples. “SUPER PRECISION” is the chronometer-grade mark. “Precision” is the standard Oyster Perpetual designation, used on non-chronometer-graded movements. “Officially Certified Chronometer” appears on examples that received the formal Swiss chronometer certification (COSC’s predecessor timing bureaus) rather than Rolex’s internal “Super Precision” designation alone.

All three configurations are period-correct. The “SUPER PRECISION” mark is the one that draws collector attention, because it is the mark that signals the highest-adjustment movement behind the dial, and because the text itself is no longer in Rolex’s vocabulary. By the 1950s the factory had consolidated on “Officially Certified Chronometer” as the standard dial-mark for chronometer-grade output. “Super Precision” falls away.

The Cal. 620N — and what “N” means

The 2764 is powered by Cal. 620N, a 9¾-ligne automatic in the 620 family. The physical specifications are documented: 26.4mm × 7.5mm, 18,000 vibrations per hour, 35 to 41 hours of power reserve, unidirectional 360-degree rotor in the Rolex Perpetual tradition, Rolex Super Balance, Breguet overcoil hairspring, nickel finish, sub-seconds register at 6 o’clock. Seventeen jewels in standard configuration.

The “N” suffix has been a source of confusion in forum commentary, which has occasionally read it as a technical grade indicator, a variant caliber number signalling chronometer adjustment or some other quality distinction. The parts-catalog evidence suggests otherwise. In the Esslinger parts listings and in the Caliber Corner reference documentation, “N” and “NA” appear as sizing codes for the 9¾L NA parts group, the dial-side measurement category used to index spare parts across the Aegler/Rolex parts catalog. The letter designates where on the parts chart a given caliber lives, not what timing grade it was built to.

That distinction matters for two reasons. First, it resolves a long-running debate in Bubbleback collector circles about whether “620N” denotes a separate caliber, a chronometer-adjusted variant, or simply a cataloging convention. It is a cataloging convention. Second, it means the grade of the 620N in a given 2764 is an independent attribute from the sizing-code suffix. The standard 620 is 17 jewels and unadjusted beyond Rolex’s baseline. The “Super Precision” 2764 dials sit on 620 movements that happened to be chronometer-graded while also falling into the NA parts-catalog group. Both things are true at once. The grade is marked on the dial (“SUPER PRECISION”) and reflected in the movement’s adjustment work; the NA suffix is a catalog index. A 620N can be chronometer-adjusted or not, depending on which example it is.

The prevailing view among informed collectors is that the sizing-code interpretation is correct. Anyone reading “N” or “NA” on a Cal. 620 movement plate and concluding they have a technically-distinct caliber on their hands is reading the wrong story into the suffix.

Case and construction

The 2764 case is a two-piece Oyster. Smooth polished fixed bezel, mid-case with the Bubbleback’s characteristic domed caseback screwed directly into it, with no separate movement-holder ring (that generation of construction ended in 1936). The screw-down crown maintains the Oyster’s waterproof claim; the acrylic crystal rides above the dial.

Case dimensions cluster at 31mm in the Phillips and Heritage catalog measurements and 32mm in most dealer listings. Lug-to-lug runs about 39mm; thickness about 13mm; lug width 19mm. On the wrist the 2764 reads as a small-to-mid-size dress watch, smaller than a modern 36mm Oyster Perpetual, domed enough to sit high on the wrist in the Bubbleback tradition.

The caseback dome is the defining external feature of the Bubbleback profile, and on the 2764 it follows the mature second-generation Bubbleback template: enough curvature to house the 620-family rotor without forcing the case walls thicker, but not as exaggerated as on the earliest Cal. 520-era examples where the movement architecture drove the dome geometry hardest. By the 620 era the rotor mass had stabilized and the dome was a known quantity.

Lugs are standard (soldered to the case in the pre-war and early post-war Rolex convention), with 19mm spacing at the strap end. The crown is a period Rolex screw-down.

Case materials

The 2764 was built in three case configurations. Stainless steel is the most common at auction and in surviving populations; the Phillips Geneva Watch Auction THREE lot (case 107118) is stainless steel. Gold shell (a layer of gold applied over a stainless steel base case, typically with a stainless caseback) accounts for the middle tier of surviving examples. Gold-plated (thin electroplated gold over base metal) examples also exist.

No solid gold 2764 example is confirmed in auction archives or dealer surveys. That distinguishes the reference from the 4467, the contemporary 18K gold Big Bubbleback Datejust, and from solid-gold examples among other 31–32mm Bubbleback siblings. Claimed solid-gold 2764 watches warrant caseback weight documentation and hallmark photography before the claim can be taken at face value.

Dial variants

The 2764 produces a wider dial variety than most single Bubbleback references of the period, partly because the production window ran over a decade and partly because the reference carried multiple retailer variants, each with its own dial configuration.

A two-tone champagne radium dial appears in the rarer surfaced examples documented through Antiquorum: champagne-toned center with a contrasting outer chapter ring, radium-lumed hour markers, typically paired with luminous baton or pencil hands. The warm champagne palette reads distinctly from the more common cream or off-white dials and is the configuration most closely associated with the Birks Canada retailer signature.

A multi-tone off-white dial with copper or gold raised Arabic numerals is the configuration Phillips presented as Lot 126 in the Geneva Watch Auction THREE (May 2016). The dial is an off-white with tonal shifts across the surface, applied raised Arabic numerals at every hour position in copper or gold tone, a conventional seconds sub-register at 6 o’clock. The Phillips example, stainless steel with case 107118 dated 1941, sold for CHF 31,250 against an estimate of 15,000–25,000. This is the 2764’s public-auction benchmark for a strong-condition example.

The California-dial 2764, documented by Bachmann & Scher, pairs Arabic numerals on the lower half with Roman numerals on the upper half, the “California” layout that Rolex used on a small number of dial configurations across the 1930s and 1940s, and that Wind Vintage and other specialist dealers have catalogued extensively on later Submariner and Explorer references. The 2764 California is one of the earlier appearances of the layout. Radium-lumed markers at the hour positions; blued steel or luminous baton hands depending on the example.

Silver/cream with luminous Arabic numerals — the “Turtle Perpetual” retailer variant. The Heritage Auctions example retailed through Zell Bros. of Portland, Oregon, carries a silver or cream dial with luminous Arabic numerals at every hour position and the retailer’s “Turtle Perpetual” mark in addition to the Rolex text. This is the single best-known retailer variant of the reference and gives the 2764 a named place in the North American retailer-signature literature that collectors of the period track.

The baseline configuration is the standard cream or off-white dial. Applied or painted Arabic numerals, Rolex coronet and “Oyster Perpetual” line at 12 o’clock, “SUPER PRECISION” or “Precision” or “Officially Certified Chronometer” mark below 6 o’clock, sub-seconds register integrated into the dial. This is the configuration that appears most often in unsigned examples without retailer provenance.

Hands across the dial variants fall into four recurring styles. Blued steel sword hands on the more austere dials; luminous baton hands on the radium-marked variants; pencil or stick hands with radium inserts on the standard configurations; cathedral hands on a smaller subset of examples, typically paired with the more formal dial layouts.

The Zell Bros “Turtle Perpetual”

Zell Bros was a Portland, Oregon jewelry retailer that carried Rolex in the late 1930s and 1940s. Their “Turtle Perpetual” designation for a 2764 variant is a retailer-specific naming convention, a local dealer’s marketing term for the Bubbleback’s distinctive domed caseback rather than a Rolex factory designation. The “turtle” reference is to the caseback dome’s resemblance to a turtle’s shell. The name appears on Zell Bros-signed dials and sometimes also in accompanying retail paperwork.

Heritage Auctions has documented at least one Zell Bros “Turtle Perpetual” 2764 in their archives, and the reference is mentioned in collector forum discussions of North American Rolex retailer signatures from the period. The practice of regional retailers applying their own nicknames to Rolex models was common in the pre-war and early post-war years. Rolex distribution was less centralized, and retailers had more latitude to present watches under their own language. Zell Bros is one of the better-documented American examples.

The Zell Bros 2764 dials are typically the silver or cream configuration with luminous Arabic numerals, paired with the retailer’s signature alongside the Rolex text. An authentic Zell Bros “Turtle Perpetual” 2764 is a cross-category collectible: a Bubbleback for Rolex collectors, a retailer-signed vintage American watch for specialists in period dealer variants, and a 620-era dress watch with chronometer-grade possibilities behind it depending on the individual example’s dial mark.

The Birks Canada variants

Birks (Henry Birks & Sons, the Canadian luxury retailer founded in Montreal in 1879) carried Rolex through the pre-war, wartime, and post-war decades. Birks-signed Bubblebacks exist across multiple references, and the 2764 is represented in their retail output by the two-tone champagne dial variants.

A Birks 2764 typically carries the “Birks” signature below the Rolex coronet on the dial, paired with the standard Oyster Perpetual text and the “SUPER PRECISION” or “Precision” mark. The two-tone champagne dial configuration associated with Birks distribution reads as a dressier, warmer variant than the plainer cream dials; the champagne palette matches the gold shell case finish when the two are paired.

Birks-signed Rolex watches from this period trade in a specialist segment of the Canadian vintage market. An original Birks 2764 with its two-tone champagne dial is period-correct, desirable, and uncommon enough to warrant retailer-signature premiums at the North American end of the auction circuit.

Auction record

The 2764’s public auction footprint is dominated by the Phillips Geneva Watch Auction THREE result, with supporting examples from Heritage, Antiquorum, and Bachmann & Scher dealer listings.

Venue Date Lot Case No Material Dial Result
Phillips Geneva Watch Auction THREE May 2016 126 107118 Stainless steel Multi-tone off-white, raised gold Arabic CHF 31,250 (est. 15,000–25,000)
Heritage Auctions — — 107524 Stainless steel Silver/cream with luminous Arabic, Zell Bros “Turtle Perpetual” signed Earliest documented case
Antiquorum — — — — Two-tone champagne radium, Birks-signed Referenced in collector archives
Bachmann & Scher — — — — California (Arabic + Roman + radium) Dealer listing, California-dial example

The Phillips Geneva Watch Auction THREE Lot 126 result is the public benchmark. Case 107118, movement 91390, dated 1941, stainless steel, multi-tone off-white dial with raised copper or gold Arabic numerals, expandable bracelet of the period. Estimate CHF 15,000–25,000; sold CHF 31,250. The result sits meaningfully above the high estimate. The configuration (strong dial, clean case, period-correct hardware) drew committed bidding, and the case number places the watch near the middle of the 2764’s production window.

The Heritage Zell Bros “Turtle Perpetual” example (case 107524) is the earliest documented 2764 serial. The retailer signature and nickname combination makes it a collector-category piece in the North American specialist market.

The Antiquorum two-tone champagne radium examples and the Bachmann & Scher California variant fill out the configuration space. No 2764 has exceeded the Phillips 2016 result in publicly-indexed sales.

Case number observations

Observed 2764 case numbers cluster in the 107000-range based on the two best-documented examples (107118 on the Phillips lot, 107524 on the Heritage Zell Bros example). Given the ten-plus-year production window and the mid-century Rolex serial allocation pattern (serials shared across contemporary references), the 2764’s own range likely extends substantially above and below this cluster. The small public-auction sample size constrains tighter mapping.

Collecting considerations

For collectors, the 2764 occupies a specific Bubbleback slot: the chronometer-grade dress variant with the “SUPER PRECISION” mark, the odd-suffix Cal. 620N, and a cluster of collector-grade retailer variants. The configuration hierarchy is legible and the price anchoring is reasonable.

The configuration hierarchy runs from most to least desirable. At the top sit the “SUPER PRECISION” dial paired with the Zell Bros “Turtle Perpetual” retailer signature on a stainless case, cross-category collectibility married to the chronometer-grade mark. Below that, the multi-tone off-white with raised gold Arabic numerals on period-correct hardware, the Phillips 2016 Lot 126 configuration and the public benchmark. The two-tone champagne radium with Birks signature is a distinctive retailer pairing, and the California dial (Arabic and Roman numerals combined with radium) is the rare dial-layout variant. Below those, standard cream or off-white with the “SUPER PRECISION” mark remains a strong baseline; the same dial with “Precision” or “Officially Certified Chronometer” is the everyday configuration.

Authentication priorities cluster around a handful of checks. The movement should be Cal. 620, with or without the “N” sizing-code suffix on the plate, a 9¾-ligne automatic with unidirectional 360-degree rotor, Super Balance, and Breguet overcoil. Architectural differences (bidirectional rotor, different rotor geometry, different bridge layout) indicate a service-replacement movement from a different caliber family. On the dial mark, “SUPER PRECISION” is period-correct and desirable; “Precision” and “Officially Certified Chronometer” are also period-correct. A 2764 with no precision-designation mark at all is uncommon and warrants closer dial examination, as refinished dials occasionally lose the fine text around 6 o’clock in restoration. Case material should be stainless steel, gold shell, or gold-plated, the three documented options. Claimed solid-gold examples require hallmark photography and caseback weight documentation. Retailer signatures from Zell Bros (“Turtle Perpetual”) and Birks are period-correct; unusual retailer marks warrant research against known North American and European retailer archives, and added retailer text on a refinished dial is a known flag. On lume, radium markers should patinate together with radium-inserted hands. Mismatched lume color across the dial markers and hands is a replacement tell, and refinished dials with relumed markers reduce value meaningfully.

The Phillips 2016 result at CHF 31,250 represents the current benchmark for a strong-configuration 2764 at public auction. Dealer asking prices for standard examples run lower; strong retailer-signed examples run higher. A clean stainless 2764 with “SUPER PRECISION” mark and period-correct hardware should anchor somewhere in the CHF 10,000–25,000 range depending on condition and dial configuration, with Zell Bros and Birks retailer signatures pushing into the CHF 20,000–35,000+ range when paired with strong condition.

Still open

Exact production total

No published figure exists for 2764 production. The ten-year window (c.1937–1948) and shared serial allocation with other Bubbleback references of the period make it difficult to infer a total from auction sample alone. Surviving case-number clusters suggest low-to-mid four digits as a plausible range, but this is inference rather than documentation.

The “N” suffix across the 620 family

The sizing-code interpretation of “N” and “NA” on Cal. 620 movements is supported by parts-catalog evidence (Esslinger listings, Caliber Corner), but the broader question of how consistently Rolex applied the dial-side NA group designation to 620 movements across all references that used the caliber is not fully mapped in public sources. Not every 620-powered Bubbleback carries “N” on the plate; not every 620N is chronometer-graded. The relationship between plate-stamped suffix, dial-mark grade, and actual timing certification warrants further documentation.

Retailer-signature corpus

The Zell Bros “Turtle Perpetual” and Birks Canada variants are the best-documented 2764 retailer configurations. Other American, Canadian, and international retailers likely carried the reference as well; a systematic survey of 2764 retailer signatures does not yet exist in the collector literature.

Solid-gold population

The absence of confirmed solid-gold 2764 examples in auction archives and dealer surveys is a negative finding. It supports the conclusion that Rolex did not build the reference in solid gold but is not conclusive in the strict sense. A solid-gold 2764 surfacing with hallmark and period-correct documentation would update this assumption.

Sources

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