Reference:3525

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Rolex 3525 'Monoblocco' — the first Oyster chronograph (1939-45), Cal. 13 Valjoux 23 VZ, monobloc Oyster case.

Chronograph → 3525

The 3525 is the first. Before it, Rolex had built chronographs (the 2021 single-pusher, the 2508 with its Valjoux 22, the 3330 with its hinged gold case), but none inside the patented Oyster. The 3525 put a chronograph movement behind a screw-down crown and a screw-down caseback for the first time, becoming the technical predecessor of everything that runs from the 6034 through the 6238 through the Daytona. Italian collectors named it twice. Monoblocco refers to the case construction, with the upper half (bezel, mid-case, lugs) machined from one block of metal and only the caseback separate. Barilotto means “little barrel,” a description of the silhouette. Both names stuck.

It is also the watch that Rolex shipped, on credit, to Allied officers held in German prisoner-of-war camps during the Second World War. One of those watches ended up at Stalag Luft III, the camp of the Great Escape. That example, with its paperwork fully intact, sold at Antiquorum in 2007 for £66,000.

Core facts

detail value
reference 3525
family Chronograph (pre-Daytona)
production 1939–1945
case diameter ~35mm
case construction Monoblocco — one-piece upper case (bezel + mid-case + lugs) plus screw-down caseback
crown screw-down Oyster
movement Rolex Cal. 13 (Valjoux 23 VZ base), 17 jewels, manual wind
layout two-register: running seconds at 9, 30-minute counter at 3
scales tachometer and telemeter
crystal acrylic
case materials stainless steel; steel + gold; 18K yellow gold; 18K pink gold
italian nicknames Monoblocco (“one block”); Barilotto (“little barrel”)
collector name The “POW watch”

Where it sits in the line

Rolex patented the Oyster case in 1926 and the Perpetual rotor in 1931–32. By the late 1930s the Oyster had become standard across the range of time-only and time-plus-date watches, but it had not yet accommodated a chronograph. The problem is obvious once stated. Chronograph movements require pushers, pushers breach the case, and a breached case is not waterproof. The 3525 answers that problem with screw-down pushers, a screw-down caseback, and a case whose upper half (the part that carries the pushers, the crystal seat and the crown tube) is machined from a single billet of metal, eliminating the jointed seams that a multi-piece construction would otherwise present to water.

Against its peers the 3525 sits as the first of the Oyster chronographs. The sister reference 3668, produced in tiny numbers in the 1940s with a reeded gold bezel, carries the same Cal. 23 VZ base in a different case construction. The 4500 of the late 1940s introduces the Tonneau case. The 6034 in the early 1950s finally adopts the screw-down pusher architecture that the 3525 foreshadowed. But as the first Rolex chronograph to enter an Oyster case, the 3525 is the pivot.

The monobloc case

The Monoblocco construction is the technical centerpiece of the reference. On a conventional three-piece Oyster, the case is made up of a bezel that screws onto the mid-case, the mid-case itself, and a caseback that screws in from below. Each interface between pieces is a potential water path sealed with a gasket. On the 3525, the bezel, the mid-case and the lugs are not separate pieces. They are one piece of metal, turned and machined as a unit. Only the caseback threads in separately. The crown and the two chronograph pushers pass through the single upper piece, each with its own screw-down seal.

Italian collectors called this Monoblocco from early on. The alternative nickname, Barilotto, comes from the barrel-like taper of the upper case in profile: the bezel zone is slightly narrower than the caseback perimeter, giving the watch a faintly hourglass shape when viewed from the side. Both names appear interchangeably in Papaleo, Pucci, and Mondani, and in modern catalog text from Antiquorum and Sotheby’s.

The case measures approximately 35mm across. In period, that was a full-sized men’s chronograph. On the wrist today, it wears small. The lug-to-lug is short, the crystal is domed acrylic, and the whole package is lighter and thinner than anything from the Daytona era. Compared to a Cosmograph Daytona of the 6239 generation, the 3525 is noticeably more restrained on the wrist and reads as a watch of its period.

The Cal. 13 and the Valjoux 23

Rolex catalogued the movement as “Cal. 13.” The designation refers to the 13-ligne size (roughly 29.5mm) of the movement blank. The base is the Valjoux 23 VZ, a lateral-clutch, column-wheel chronograph with 17 jewels, a running seconds register at 9 o’clock and a 30-minute counter at 3 o’clock. No continuous hour counter; the 3525 is a two-register watch. Central chrono seconds. The balance is screwed; the bridges carry “Rolex” and “17 Rubis” signatures in most examples.

The Valjoux 23 was one of the most respected chronograph bases of the 1930s and 1940s, used by Patek Philippe, Vacheron Constantin, Breguet and others. Rolex bought the base from Valjoux and finished and cased the movements in-house. The “in-house” framing sometimes applied to Rolex chronographs of this era is inaccurate for the 3525. Rolex did not manufacture the chronograph module. Rolex specified, finished and housed it.

The movement’s configuration sets the reading logic of the dial. Elapsed minutes read at 3 o’clock. Running seconds read at 9 o’clock. Elapsed seconds read off the central hand. The outer chapter carries a tachometer scale for speed calculation and a telemeter scale for distance-to-sound-source calculation. Both scales were standard period equipment on a sports chronograph, and both persist through the Daytona era that follows.

Dial variants

Across roughly six years of production and four case metals, the 3525 accumulated a full range of dial configurations. The common patterns:

Silver / silvered dial. The most common configuration on stainless steel cases. Applied baton or Arabic indexes, blued steel hands, printed tachometer and telemeter scales on the outer track. The Sotheby’s 2020 Important Watches Part II example (case 372,822, c.1945) carries this dial.

Black gilt dial. Glossy black with gilt (gold-toned) printing for scales and signatures. The Sotheby’s 2019 example (case 186,144, c.1942) is described in the lot text as “glossy black gilt.” This variant tracks the same gilt-printing convention that Rolex used on contemporary time-only Oysters before the matte-dial transition of the mid-1960s.

Salmon / pink matte. Standard on pink gold cases. The Mondani Collection example (case 147,854, 1940) has a matte pink dial with printed baton indexes, Arabic 6 and 12, and blued steel bâton hands.

Two-tone. Contrasting center and outer chapter, in the Art Deco dial language common to late-1930s and early-1940s chronographs.

Tropical black. Black dials that have shifted to brown under UV exposure. As with later Submariner and GMT-Master gilt dials, tropical 3525 dials command a substantial premium when the fade is even and the printing remains crisp.

Military-spec black. Matte black with applied luminous markers. This is the configuration that appears on the POW-delivered examples; the Nutting and Brownlee watches both carry black dials. Whether the black dial was specified by the recipient, selected by Rolex for the POW program, or simply the stock option for the steel 3525 in the early 1940s is not documented.

The POW program and the Nutting watch

The 3525’s second identity is as the “POW watch,” the Rolex chronograph that Hans Wilsdorf shipped to Allied officers in German prisoner-of-war camps during the Second World War.

The mechanism was straightforward. British and Commonwealth officers captured by the Germans retained the right to correspond with the outside world, including the right to order goods by mail. Rolex, a Swiss neutral-nation company, could legally ship watches to the camps. Wilsdorf wrote to officers directly and offered the arrangement: order a watch, take delivery in the camp, pay after the war. The policy was underwritten personally by Wilsdorf. Some accounts frame it as gratis; the Antiquorum lot text for the Nutting watch reads “sold gratis,” meaning shipped without pre-payment rather than given away. The distinction mattered to Wilsdorf: the watches were sold on extended credit, not donated.

The best-documented example is the Nutting watch. Corporal Clive James Nutting of the British Army was captured and interned at Stalag Luft III, the German Luftwaffe-run prisoner camp in Lower Silesia (today Żagań, Poland). Stalag Luft III is the Great Escape camp, the March 1944 tunnel breakout by 76 POWs from Hut 104 that was later dramatized in the 1963 film. Nutting was a shoemaker by trade and a signals specialist, and he was part of the escape-planning committee from early on. He did not use the tunnel itself before its discovery, but he made civilian belts, shoes and briefcases for escapers from leather stolen from German officers who brought their kit in for repair.

Nutting ordered a Rolex. The watch is a steel 3525 Oyster Chronograph Antimagnetic, serial 185,983, made in 1941 and shipped by Rolex on credit in 1943. The Antiquorum lot text records a shipping date of 8 July 1943; Rolex Magazine’s article on the watch records a delivery-to-camp date of 4 August 1943. Both can be true: one is the Swiss ship date, the other the camp arrival date. By August 1943 Nutting had a Rolex chronograph on his wrist in Stalag Luft III, eight months before the Great Escape.

Nutting kept the watch for the rest of his life. He repatriated to Britain after the war, later emigrated to Queensland, Australia, and died there in 2001 at age 90. His archive stayed with the watch: the numbered receipt from Rolex, the numbered guarantee, the Rolex envelope, three letters from the Rolex Watch Co. signed by Hans Wilsdorf himself, and Nutting’s own correspondence and photographs from Stalag Luft III. The whole package sold at Antiquorum in 2007 for £66,000.

Other POW-provenance 3525s surface periodically. The Brownlee watch (USAAF 1st Lt Leon W. Brownlee, held at Stalag 7A in Moosburg, Bavaria, freed April 1945) appeared at Antiquorum Geneva in May 2023 with an estimate of EUR 62,000–102,000. Phillips published an article on the Dickins 3525 (RAF Wing Commander Douglas S. Dickins). Dealer and forum listings carry additional named-POW examples. The Rolex POW archive is incomplete; no full list of delivered watches survives in public. The documented examples form a small, coherent corpus.

On the specific claim that the Nutting 3525 was used to time the Great Escape itself: Nutting was on the planning committee, the 3525 is a chronograph with a 30-minute counter, and the watch was on his wrist in the camp at the right time. Whether it was actually used to time guard patrols or to cue escapees through the tunnel is not documented in the Rolex archive or in Nutting’s own writings. The connection is circumstantial, strong enough to mention but not to state as fact.

Auction record

The 3525 appears regularly at major auction houses. A representative set of lots:

Venue Date Case No Material Dial Notes Result / Estimate
Antiquorum Geneva (Mondani Collection) 14 May 2006 147854 18K pink gold Matte pink, bâtons Illustrated in Mondani —
Antiquorum Geneva 2007 185983 Stainless steel Black Nutting POW, full archive, Wilsdorf letters £66,000
Antiquorum New York 12 Jun 2012 — 18K yellow gold — Standard Monoblocco —
Antiquorum Geneva 13 May 2018 — 18K yellow gold Black Lot 313/157 —
Sotheby’s (Important Watches) 2019 186144 Stainless steel Black gilt (glossy) Rivet bracelet; c.1942 Est. USD 12,000–18,000
Sotheby’s (Important Watches Part II) 2020 372822 Stainless steel Silvered c.1945, second production series Est. CHF 20,000–30,000
Antiquorum Geneva May 2023 — Stainless steel Black Brownlee POW, USAAF Stalag 7A Est. EUR 62,000–102,000
Antiquorum Geneva May 2024 47267 18K pink gold Black Monoblocco Est. USD 89,000–156,000
Antiquorum Hong Kong 1 Jun 2024 — 18K pink gold — Retailed by Verga Est. CHF 82,000–140,000

The price spread tracks two primary variables: metal and provenance. A plain-dial steel example without special provenance trades in the low five figures USD; a pink gold example trades in the high five to low six figures; and a fully provenanced POW example with Wilsdorf correspondence clears six figures. The Nutting watch at £66,000 in 2007 remains the anchor result for the reference, and that figure would clear multiples today, both because the market has moved and because the corpus of comparable paperwork-intact POW provenance has not grown.

Case-number clusters and dating

Case numbers observed on documented 3525s span from the ~140,000s (1940) through the ~370,000s (1945). That range is broad because the 3525 was produced continuously for six years, shared serial allocations with other Rolex references of the period, and included multiple metal variants produced at different cadences. The Sotheby’s 2020 lot text describes a “second production series (1942–1946)” for case 372,822, a distinction that suggests two generations of 3525, potentially with minor detail changes between early and late production. Specialist research on the precise transition point has not been published in accessible sources.

The Alpha Hands 3525 Case Number Project aggregates documented serials in a searchable database. Its working estimate for total production exceeds the older dealer-literature figure of ~200 steel examples; actual steel production is likely in the low four figures, with gold examples adding several hundred more. A reasonable working total across all metals is ~2,000–2,500 pieces. Firm archival documentation does not exist.

Authentication notes

The 3525 is old enough that condition and originality variance is extreme. A buyer’s checklist on period-correct examples:

Case geometry. The Monoblocco construction should be visible in profile: no interior seam where a bezel would meet a separate mid-case. The caseback is the only separable part. Pushers should be flat round buttons that screw down; unscrewed, they should rotate smoothly and spring back firmly.

Caseback markings. The inside of the caseback on a period-correct 3525 carries Rolex-specific stamping including “Oyster Watch Co” and period reference and model codes. Over-polished casebacks with the stamping worn away are common after 80 years of ownership.

Dial. Refinished and replacement dials are the single largest originality variable on vintage 3525s. Period-correct printing on the tachometer and telemeter scales is fine and crisp; heavy, thick printing is a refinish indicator. Applied indexes on gold cases should match the case metal tone. Black gilt dials with even patina and intact gilt printing carry substantial premiums; the same dial refinished is worth a fraction.

Movement. Cal. 13 (Valjoux 23 VZ) should be signed on the bridges. Movement serials should sit in the documented range. Replacement movements transplanted from a non-Rolex Valjoux 23 host exist; the movement bridges should read “Rolex,” not “Valjoux.”

Provenance paperwork. For any 3525 offered with POW provenance, the physical documentation is decisive. Wilsdorf letters on period Rolex letterhead, numbered guarantee, numbered receipt, and POW archive material collectively make the provenance. Verbal family-lore provenance without paperwork is treated with skepticism in the market.

What the 3525 established

Two features of the 3525 persist in Rolex chronograph production for decades after the reference itself ends.

The Oyster chronograph case. Every Rolex chronograph after the 3525 is waterproof. The 3668, 4500, 6034, 6234, 6238 and the Daytona family all descend from the waterproofing solution that the 3525 solved first. The specific Monoblocco construction does not persist (by the 6034 generation Rolex is using multi-piece Oyster cases with screw-down pushers) but the principle does.

The sport-chronograph identity. The 3525 is a chronograph with a purpose, not a dress complication. Tachometer and telemeter scales, screw-down crown, screw-down pushers, 17-jewel lateral-clutch movement, rivet Oyster bracelet as period-correct strap choice. That package, a functional chronograph designed to be worn hard, is what runs straight through to the Paul Newman Daytona and beyond.

Collecting considerations

The 3525 occupies a specific place in the vintage Rolex market. Compared with a Daytona, prices are lower, the collector pool is smaller, and the academic literature is thinner. Compared with a generic 1940s chronograph, the Oyster construction, the POW history and the Rolex signature carry a meaningful premium.

Metal matters most. Steel 3525s are the most historically significant (most POW examples are steel) and the most commonly encountered. Pink gold 3525s are the dress-watch alternative and command substantial premiums. Yellow gold sits between. Steel-plus-gold two-tone examples are the rarest configuration and trade inconsistently.

POW provenance is a category of its own. A paperwork-backed POW 3525 is effectively a different watch from a civilian-delivered 3525 of the same specification. The price gap can be 5–10x. For collectors, this is a market where documentation is doing enormous work, and the documentation must be convincing.

Dial originality is the biggest variance driver. After metal and provenance, the dial determines price. Untouched original dials with even patina command multiples of refinished or replacement dials. For the black gilt variant specifically, the fade pattern and gilt printing intactness are the primary inspection points.

Service history. At 80+ years old, a 3525 that has been serviced periodically is in better mechanical shape than one that has not. Heavy service can also mean replaced mainsprings, replaced chrono coupling parts, and in some cases replaced movement components. A known service history from a reputable vintage Rolex watchmaker adds value.

Still open

Production total

No factory production figure is published. The low-end estimate of ~200 steel examples, which circulated in earlier dealer literature, is not consistent with the surviving population observed in the Alpha Hands case-number project. A working estimate of 2,000–2,500 total across all metals is plausible but not archivally confirmed.

POW delivery census

No full list of Rolex watches delivered to POWs survives in public. The Nutting, Brownlee and Dickins examples are documented; other named-POW examples circulate in the market; but the total number of 3525s delivered to prison camps, versus the number delivered to officers who happened to be POWs but where the Wilsdorf-credit program was not the mechanism, is not published. Rolex’s internal archives on the program have not been opened.

Nutting watch delivery date

The Antiquorum 2007 lot text reads “sold gratis on 8 July 1943.” Rolex Magazine’s account reads “delivered to Stalag Luft III on 4 August 1943.” Both dates appear to be real events in the shipping-and-delivery chain; the specific reconciliation has not been documented in public.

Sources

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