Perpetual Calendar 1518

The first perpetual calendarPerpetual calendarA calendar mechanism that accounts for different month lengths and leap years. chronographChronographA watch function for starting, stopping and resetting an elapsed-time measurement independently of the ordinary time display. made in series, launched at Basel in 1941. 35 mm case with long downturned lugs, concave bezelBezelThe frame surrounding the crystal at the front of a watch. and rectangular pushers. Its layout – day and month windows under 12, minute counter at 3, seconds at 9, date and moon at 6, base-1000 and fifth-second track – set the pattern for every successor.