Vintage Watch COSD Military Chronometer — WatchProSite Forum Digest

Lépine · 2025-07-20T23:47:40Z

Explore the Longines C.O.S.D. dive watch, a rare D-Day artifact. Lépine details its history, unique features, and the challenges of collecting these vintage military timepieces.

Lépine

WPS member · Horological Meandering forum

31 replies3194 views14 photos

Lépine, a respected authority on military timepieces, shares an in-depth look at the Longines C.O.S.D. dive watch, a historically significant piece once misidentified for decades. His post not only showcases a remarkably preserved example but also delves into the meticulous research that uncovered its true purpose as a shallow-diving instrument for D-Day clearance divers. This article highlights the importance of dedicated collector research in correcting historical records and appreciating the nuanced details of these rare watches.

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The Combined Operations preparations for D-Day are fairly well known. Until not that long ago, not much was known about this bit of history. The watch was misidentified as a British Army Paratrooper watch for decades. It took several MWR members digging through the IWM archives to find the photos proving these were dive watches made for the intent of providing clearance divers with shallow diving watches.

Here in my opinion is a very nice tropical COSD with all the original gaskets and one of the best examples of a truly and appropriately used dive case.

The proper original dials from Longines have raised printing.

There is wear around the top of the case from rubbing against the dive suits.

Here is an original gasket.

These are original movement rings.

The original markings were not stamped or engraved the traditional way. These were marked with a spinning drill bit.

There is about 100 surviving COSD. Unfortunately, there are more made every year.

Gold, possible prototype, MOD, and Original Radium Big Crown.

Key Points from the Discussion

The C.O.S.D. watches were issued to the Combined Operations Pilotage Parties (COPP), an elite, covert unit of fewer than 200 men from the Royal Navy and Royal Engineers, who conducted reconnaissance for D-Day and other amphibious landings using midget submarines and canoes.
Lépine has cataloged and tracked over 100 C.O.S.D. watches over 10 years, compiling a comprehensive serial number project available on MWRforum.net, which includes Longines factory records for these references.
Authentic C.O.S.D. watches are often counterfeited; collectors must be vigilant for 'frankenwatches' with aftermarket hands, incorrect radium dials for MoD versions, small crowns, or mismatched casebacks.
The C.O.S.D. watches were sometimes repurposed after military service, with movements placed into dress watch cases and sold as military surplus to entities like BAS and BOAC.
The prevalence of fakes and frankenwatches raises questions about the motivations of counterfeiters, suggesting that even a small number of highly informed collectors might still create a market for such deceptive pieces.
Building a network of fellow collectors and dealers who share similar interests is crucial for acquiring rare watches and accessing private research materials, often leading to specific offers for desired pieces.

The Discussion

aperna

Jul 21, 2025

Outstanding piece of history

LÉ

Lépine

Jul 21, 2025

Thank you!

Finding a nice tropical COSD has been a goal

EinPA

Jul 21, 2025

Thank you for this

Informative and detailed study. So there are many fakes?

LÉ

Lépine

Jul 21, 2025

Yes quite a few. And many franken watches

fmc000

Jul 21, 2025

I have a question, if you don't mind.

These are very special items, my understanding is that there are only a few collectors around the globe that can really appreciate the historical significance of them. I suppose that these collectors are very well informed and therefore can (easily?) identify fakes and/or frankens. Hence my question: what's the point of making those fakes? Do they fetch such a premium that just making one can be worth the effort for the scammers?

LÉ

Lépine

Jul 21, 2025

Typically £10,000-£13,000 for all correct

You need to add 30% buyers premium to the below bid results Below is a questionable specimen in my opinion. Aftermarket hands. Dial is MoD at best but the whole watch is radium which is wrong for an MoD. It has small crown. Caseback doesn't match the case. I.E. it's a frankenwatch.

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