Oooo, that's interesting. As to Alex's question about whether we're collecting movements, well, why not? These are the heart of our watches after all and Heuer trialling a faster frequency movement is surely of historical notability to a Heuer collector.

Ask the seller if they can provide photos of the caseback to see if they show the same sort of markings as Sandra's nice example. None of my 1153s are in the same serial number range as Sandra's Autavia, but I'll give them all a listen - you'd think they would want to use the prototype movement in all the relevant cases to check for NVH or other issues specific to that case. Or at least I would if it was doing it now, and sometimes it's risky to extrapolate what I would do now to what Heuer would have done in the 60s and 70s!