While I'm generally a sucker for a micro-rotor, I also have a major soft spot for the AP caliber 2120 and its derivatives. Add the engraving on the AP movement and the open dial that lets you see it from both sides, and teh deal is sealed. (Also, heretically perjhaps, not a huge fan of the dial layout on most PP perpetual calendars, this one included. Sue me. ;-D)