Damas GSTP Military Pocket Watch – Service & Repair

Alan sent me this interesting Damas GSTP Military Pocket Watch for repair and service. The watch was a non runner and also required a crystal replacement.

GSTP stands for General Service Trade Patterns, and designates watches which were issued to the military forces during the World War Two era. I always like to work on old military watches, it is a nice feeling to have a piece of history on the bench.

This particular watch is signed “Damas”. Other manufacturers also produced GSTP pocket watches (e.g. Buren, Jaeger Lecoultre, Leonidas…), with different movements but all are very similar in appearance (large dial Arabic numbers designed for legibility, subdial for seconds hand at 6). This, in my view, makes them very interesting and collectable.

Damas GSTP Military Pocket Watch Service




You can see the G.S / T.P marking on the back, as well as a serial number and the broad arrow logo.




Opening the snap-on case back reveals the movement. The ratchet wheel, like the dial is signed Damas.Damas-beguelin-BTC



Damas was a trading name of Swiss company Beguelin. The 15 jewels movement is stamped BTC , the trademark for Damas and Beguelin.



With the movement exposed, I conduct an overall appraisal of the condition of the watch, and two issues quickly become apparent, and explain why the watch is not running:

– The watch does not wind. This is only a minor issue and will be easily rectified, as I can tell the click spring has been incorrectly assembled, preventing the mainspring from storing energy.

– More problematic, the end shake on the balance wheel is far too great, a tell-tale sign of a broken balance staff (the axis of the balance). I will get back to that later.

I now proceed further with disassembly. I remove the front bezel. 

Behind the cracked and faded glass lies beautifully preserved hands and enamel dial.

I start disassembly with the dial side after removing the movement from the case.


This is a good quality movement, with a nice perlage finish on the plate. The keyless work parts are made of machined steel, not the cheaper stamped metal you find on most mass produced movements nowadays.




I proceed further with removal of the parts on the dial side.

I now move on to the other side of the movement, starting with the ratchet wheel, already taken out on the photo below (you can see the incorrectly fitted click spring I mentioned earlier, the indent under the click is not “catching” it).

I remove the transmission wheel and the barrel bridge.



I then disassemble the train bridge and the associated wheels, and remove the barrel. This gives us a nice view on the “sagging” balance wheel.


After removal of the balance wheel, the issue I suspected is confirmed….




Broken pivot on the balance staff.






It is, in fact, broken on both sides. Note the lovely Breguet overcoil type hairspring, something you only find in expensive watches nowadays.




I carry on with the service for now. The watch is now fully stripped ready for cleaning.Beguelin-BTC-Movement-Disassembled

After cleaning and detailed inspection of all parts, I start with the lubrication and assembly of the mainspring and barrel assembly.

The train wheels located on the plate, with their pivots placed in their respective holes. They are all jewelled apart from the centre wheel.



The train and barrel bridge are now in place.





Transmission wheel and ratchet wheel are fitted to the barrel bridge.




I then re-assemble the dial side.




And this is as far as I can take re-assembly for now, until I can source a replacement balance staff. The project is temporarily on hold, and all parts are placed safely under cover.

The required part is now obsolete with the various manufacturers.

My plan to get around this was to source another movement to use as a donor to replace the balance wheel assembly, as I found a loose movement at a good price on an auction site. Unfortunately, the plan was short lived as the donor movement had suffered a similar fate to Alan’s watch, a broken pivot on the staff.

Thankfully I found a seller in Germany who had 2 NOS (New Old Stock) staffs. Needless to say I bought them both (it will be the opportunity to fix the donor movement as well).

A couple of days later, I receive the new parts, and I can resume the project. I start stripping the balance wheel assembly to remove the broken staff.

Here is a photo of the new staff next to the old broken one.


And next to a twenty pence coin for scale… given their size, it is easy to understand how vulnerable the pivots are.  The movement on this watch does not have the shock protection you commonly find in more modern mechanical watches.



The new staff is carefully riveted to the balance wheel with a staking set and a number of punches.

And I can finally complete the assembly of the movement. After the service the watch is running very well with a very healthy amplitude of the balance.

I fit the movement in the case, and install dial and hands. Unfortunately, this is as far as I got with my photos, I foolishly forgot to take pictures of the finished article. It is a shame as the watch looked fantastic with the new crystal fitted!

UPDATE – Alan has very kindly sent me some pictures of the completed watch, so I can now include one here for all to enjoy. I think it looks stunning! (Photo watermarked with Alan’s blessing).Damas GSTP Military Pocket Watch WW2 - Serviced

I am very pleased with how this project has turned out, it has not been straightforward due to the availability of parts (as is often the case with vintage watches) but it was well worth the effort.

I would like take this opportunity to sincerely thank Alan for entrusting me with this great  project, and kindly providing me with the closing photo of this article. It has been a real pleasure to work on this piece of history.


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4 Replies to “Damas GSTP Military Pocket Watch – Service & Repair”

    1. Well I have some good news Robert: Alan, the owner of the watch, has very kindly emailed me some beautiful pictures, so I will be making an update shortly!

    1. Hi Ben
      It is a 19 lignes movement from DAMAS / Beguelin / BTC, but I could not find an exact reference number for the movement. Drop me an email if you are stuck I will have a staff reference in my notes somewhere.

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