2 Answers

The movement, once again, is link in-house and runs at 21,600 vph, in 47 jewels; in addition to the perpetual calendar, there is also a link minute repeater and a tourbillon regulator. Sticklers for terminological precision will recall that traditionally, "grand complication" means a perpetual calendar, repeater, and split-seconds chronograph, but I think we can give Cartier a pass on this one given the complexity link on display.

We also see the moon-phase at twelve, and the continued use of a peripheral date display. Sales of these three models would begin in 1959. While certainly a complicated way of link showing the leap year, this was the first time it had been done by any brand in series production, and you don't have to look link all that closely to see these later 5516s as something of an aesthetic and philosophical foundation upon which AP has built link much of its modern success.