The 5207 Grand Complication features the base movement from the firm’s 3939 minute repeater/tourbillon, but the perpetual-calendar module is a completely new development that makes two improvements to the complication. The month, day, date, and leap year are shown in apertures rather than in the confusing array of sub dials common to many models. And unlike conventional indicators that can take hours to register a new date, these change instantaneously at midnight. True to longstanding tradition, the somewhat minimal exterior belies the sophistication and rarity of the movement inside.
