Hi CC
Many thanks for your thoughts.
The Eb*y one is just a random example (I have no opinion on whether that particular one is correct) but there are quite a few timers / clocks seen from time to time on military watch sites that conform to that general pattern: that is, a mechanical clock that can operate electrical contacts presumably at a set time.
It is not a bomb timer, indeed, which resemble stopwatches with a variety of different graduations / markings.
There seems to be a consensus among clock / watch collectors that the above type of device had something to do with aerial reconnaissance- I can't see it myself, hence the query.
Thanks for your reply,
CH