Zenith Pocket Watch Service

This week I am featuring the restoration of this Zenith Pocket watch, belonging to my wife’s uncle.

The watch dates from the early 1900’s. It was in quite a sorry state, barely running, and missing the minute hand, and most of the hour hand. The glass was also missing. However the dial and case were in remarkably good condition, making this watch an ideal candidate for a light restoration.Zenith Pocket Watch

The case is a lovely two-tone niello silver. The inside is marked “Grand Prix Paris 1900”, along with some technical information about the watch. It commemorates the gold medal award Zenith received at the Universal Exhibition in Paris in 1900. Zenith Grand Prix1900


There are hallmarks on the case.



0.800 indicates the purity of the silver.





Grouse Hallmark



The grouse mark is an official Swiss hallmark for silver watch cases of that era.





I start the service by removing the movement from the case, and removing the dial and what is left of the hands.Pocket Watch Service


I then disassemble the dial side.Zenith Patent 30751 Dial Side


I move to the upper side of the movement. There is a patent number 30751 identified on the ratchet wheel. It was filed in 1904 and, according to my research, relates to the stem mechanism.  There is also another patent identified on the regulator, more on this later. Zenith Calibre 30751 patent


Zenith Pocket Watch Movement



After removal of the ratchet wheel and transmission wheel, I take out the barrel bridge and the train bridge, which exposes the train wheels.




The movement is now fully disassembled. The balance end stones have been removed, and the balance placed back on the plate to protect it during the ultrasonic clean.Zenith 30752 Disassembled


The parts now looking much better after cleaning.Pocket Watch Clean Movement Parts



Zenith 30751 Mainspring



I install the carbon steel mainspring back into the barrel.




I rebuild the train, and keyless work, which is located on the upper side of the plate on this movement. I suspect its design is covered by patent number 30751 identified on the ratchet wheel. 


Barrel bridge and train bridge are now in place.




And finally the escape wheel cock now in place to complete the train.





I then re-assemble the escapement. The balance is a bi-metallic compensated type, fitted with a blue Breguet overcoil, it is very nice indeed! The regulator is an ingenious cam disc system. It was registered under patent number 27541 in 1903 by Hermann Roost in Switzerland. You can rotate the disc for micro adjusments of the regulator index, which allows great precision when regulating the watch.Zenith cam disc regulator

The watch is now fully reassembled, so I need to take care of the cosmetic issues. First of all I fit a new crystal, since the original one was missing.

I then source new hands. I could tell from what was left of the hands that the watch was very likely fitted with gold Louis XV type hands, so this is what I am going to go for here.Replacement Hands Pocket Watch

Unfortunately, the only hands I can source do not match the diameter of the hour wheel and cannon pinion perfectly. I really want this type, to remain faithful to the original design so I have to do a bit of adjustment to make things fit properly: the hour hand pipe is slightly too large, whilst the minute hand hole is slightly too small.

Closing Hour Hand pipe



First I close the hour hand hole with a suitable punch.





I then broach the minute hand hole to the correct diameter. Very slowly, with plenty of trial fit, as it is all too easy to go past the point of no return if too much material is removed.Broaching Minute Hand




Finally I take care of the damaged sweep seconds hand.





The bend is carefully removed using tweezers. After all of this, I come across another snag: the seconds hand fit is too loose on the seconds wheel arbour.



I don’t think I have ever encountered so many issues with hands on the same watch!

The seconds hand pipe is very carefully tightened with a high precision vice. An expensive tool, but well worth it when you need to work on something that is irreplaceable. Tightening pipe on seconds hand


The light restoration of this watch is now complete. The movement is keeping remarkably good time in both horizontal and vertical position after the service, and the amplitude is very healthy, above 300deg. I am very happy with how this project has turned out, the watch is a thing of beauty, and it should prove a reliable timekeeper for the years to come.Zenith Pocket Watch Serviced and Restored





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