Well...not so much a repair as made a spare part...and not so much a spare part as a part to replace one I lost due to my hamfisted buffoonery during a restoration!
During reassemby, the tiny ratchet click spring living under the barrel ratchet click flew off & is now probably orbiting one of Saturn's moons. I'll certainly never see it again and it was so small, I didn't even bother to look for it.
So what to do? It struck me that the spring was made of click wire not unlike that of my guitar strings so I snipped a bit of excess off above the tuning peg (for those interested it was the top E string, Adagio light-gauge, I tried the B string first but it was too thick).
Anyway, I was able to fashion it into shape & it works. I doubt if George Daniels would have approved but the watch is an antique Swiss made pocket watch so buying spares was not an option.
So, when you change your guitar strings keep them, you never know when they'll come in useful!