We can be certain that this new movement 855P in the Emperador Coussin case is Piaget's first regular production in-house designed and manufactured perpetual calendar automatic model (with 2nd time zone). So, the new early adopters of the 855P will hold part of Piaget horological milestone.
Despite making movements for others since 1874, Piaget did not encase them as signed Piaget" watches until 1940.
Perpetual calendar (some skeletonised) movements were encased in Piaget watches but in very small series or special orders; I found documentation of examples of pocket watches (1983) and wristwatches (1981) but am not sure of the ebauche makers.
The closest Piaget calendar model were "complete calendar" with moonphase wristwatches using the 27P movement as a 250-piece limited edition on leather strap in 1985 and an all-gold case and bracelet series of 10 watches in 1986.
Regards,
MTF