What a terrible shame, last week you could have purchased off eBay a totally original Smiths MA, 3" 8 day clock, not functioning, for parts only, it sold for the bargain price of £1083.00 + £5.00 postage, then for a mere couple of hundred quid you could have had it restored to give you days or even weeks of inaccurate and unreliable timekeeping, a fool and...........
The Smiths MA is not the correct clock case or internal mechanism (I have one removed by my father in 1950 from his 1931 Austin 12/4 - can anyone tell me where to get a main spring for it?). The mechanism used on Rudge and Vincents was more sophisticated, and is the same as used on expensive cars. It's more compact and robust, and can fit in a 2" case, as fitted to tank dash panels on some '30s bikes. They usually have a domed cover glass.
These clocks sometimes come up on EvilBay, but are very expensive. I paid far too much for one which had been in a Bentley glove-box lid. It has a mounting flange around the clock body for screwing it into the wooden lid, and is not waterproof, having openings on the back for the adjusters.
Despite the stronger mechanism, the ones fitted to Vincent forks got shaken apart - that's why they are so rare. It would be vastly better to mount one on the handlebars somewhere so that it is not undergoing suspension shakes, on top of engine vibration.
Having spent far too much on one of these clocks, I think I would have been better off to buy a replica 2" case of the type intended for motorcycles, with a quartz movement, and bolt it to a handlebar clamp. That's hindsight for you.
Paul