Perpetual Calendar 5004

The first serially made 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. with split secondsSplit-seconds chronographA chronograph with two superimposed timing hands. One can be stopped to read an intermediate time while the other continues; releasing the stopped hand makes it catch up and run together with the other again. This allows comparison of events that start together., the split button in the crown. Based on the 3970, with a slightly thicker and 0.8 mm larger case; leaf hands; about 12 made a year.