An ETA 1168 powered chronostop - but not the cheap pin lever type. Holding in the top button holds the hand, pushing in the bottom is the flyback. Sold for timing things under a minute, such as pulsation and I guess short races. Unlike the cheap chronostops, the watch continues to run and keep time, regardless of button pushing. Its quite an interesting thing, and apparently not too many were manufactured.
There was no movement shot on the ebay listing, so I took a gamble, gamble paid off, there could have been something nasty inside.
bidfun-db Archive: Watch Movements: ETA 1168
Arrived today, all running well and functioning correctly.
New period sympathetic strap, and on to the wrist.