The Ronda 9037-21 watch movement, used from 1946 to 1974, exhibits certain variations depending on the period of production. Early samples of this movement featured a Breguet hairspring, whereas late samples were equipped with a flat hairspring and a mobile stud carrier. Another notable feature is the optional Triovis regulator. The Ronda 9037-21 movement offers a range of functions including a manual-wind chronograph with 60-second, 30-minute, and 12-hour counters, controlled by a pillar wheel mechanism. Additionally, it includes a sub-second function and the ability to display the day and month, both of which can be set using a pusher located at 10 o'clock. A deeper push of the same pusher allows adjustment of the day. To set the date, a pusher positioned at 8:30 o'clock is utilized.