Slimline Perpetual Calendar Manufacture

Advance the calendar through a short month

Wind the date forward to the end of a 30-day month and continue. A perpetual calendar steps straight to the 1st; an annual calendar handles most short months but fails February; a simple calendar shows a 31st and needs correcting. The leap-year indicator should also advance in step with the year subdial. This is the definitive test of the complication and it takes minutes, not months — the calendar can be advanced by hand.

A manufacture caliber should be visible and should be one

The display back exposes an in-house movement with the perpetual-calendar works. A watch carrying calendar subdials over a Sellita with a bolted-on module is a different and much cheaper object; the module construction is visible from the back as a separate plate carrying the calendar works above the base movement.