quattro[Moderator]
20315
I'm not completely sure, but here's what I found:
According to Hodinkee, the "double P" crown was introduced for the caliber 12-600 AT, which, according to Revolution dates back to 1953.
And, according to
watch-guy.com, the calatrava was added to the plain crown around 1955.
I hope this is good information: you can check all the links for yourself...
Best, Emmanuel
credit: Hodinkee