The Cortebert 603 is a manual-wind chronograph watch movement that was produced from 1937 to 1970. Over 3.5 million units of this movement were manufactured during this period. The movement featured various chrono mechanisms, with parts that were often interchangeable. It shared minor differences with the Landeron 80, allowing for modified parts to be used interchangeably between the two. In addition to the chronograph function with a 60-second counter and 30/45-minute registers switched by a cam, the Cortebert 603 also included a sub-second display. It further incorporated additional functions such as a tag pusher located at 9 o'clock, a date hand at 6 o'clock with a pusher at 8 o'clock, and a month indicator with a pusher at 2:30 o'clock.