...when you say "It's true that no two Observatoires are exactly alike", as there would appear to have been at least two or three manufactured to the same spec as the piece which features on KV's website (if various owners' scans and posts are anything to go by), but undoubtedly the greatest number differ from each other in some small (different hairspring) or not so small ( the 'Jordao' watch; Clang's SS case; the 'Stealthatoire') way.
It would be just too delicious for words to see all of the combinations in one post, or one book, or at a gathering of the custodians!! Presumably Kari is keeping track of the specs to which each piece is manufactured. Do you happen to know if that is so?
Maybe a 'roll call' is in order! ;-)
Cheers,
pplater.