Montecarlo 7031/0

First-generation Oysterdate chronographChronographA watch function for starting, stopping and resetting an elapsed-time measurement independently of the ordinary time display., introduced in 1970: Valjoux 7734 manual movementMovementThe working mechanism inside a watch or clock., pentagonal Home Plate markers and a black Plexiglas tachymeterTachymeterA chronograph scale that converts the time taken to travel a known distance into average speed. The distance and scale units must correspond. .