Indeed, the 857 probably predates the Vulcain, and is likely the first waterproof alarm.
However, I think you will reckon that, even more so than the 859, the 857 is pretty pointless for serious diving (I think it was even called 'skin diver' at that time).
So, I don't think that any of the vintage mechanical 'diving alarm' watches (whatever brand) did really see any use by real divers, back in the 1960's, or even in the more modern times.
For example, the Cousteau team was documented in many photos to have worn tens of different watches (including lots of Blancpains, Rolex, Omegas among others), but none of them were alarm watches, which tends to prove that the alarm was probably not so much required by serious divers.
They are very nice to collect though, as definitively have a lot of charms !!