I like this watch, very nice appearance and classic Breguet style hands.
Caliber 240 is very unique. It was produced first in 1977 and it had no serious modifications till now. It is mystery how PP managed to make microrotor with such robust construction. I guess, that PP invited command of designers from UG. If you compare Universal Geneve 66 and PP240 you can notice too many common things in conctruction. So my opinion - PP240 - is the best modification of UG66 line, that's why it is so robust and successful.
I know Arnaud Tellier (ex PP museum director in Geneve) and talked with him about 240. He told me, that 240 was designed especially for thin perpetual. Approx in 1985 was the first thin perpetual 3940, you can see the earliest versions in PP museum.
As to 5040 - tonneau version of 3940. First watches produced in mid of 90s. So mine is one of the first watches - produced in 1995.
The watch is really interesting. The movt is only 3.8 mm high, so it is one of the thinniest perpetuals in the world (the watch complete is approx 9 mm high). PP specialists managed to make such a thin caliber placing all parts of calendar straight on the main plate. Among other watches I know only AP with caliber with perpetual calendar 4.0 mm height, but it has no 24-h hand and has no leap year indicator. Also it has no month setting push button, that makes using perpetual not so comfortable.
The proof of the pudding is in the eating...