The Ronda 1317-21 watch movement, manufactured between 1937 and 1970, has produced over 3,500,000 units. This movement features a manual-wind chronograph with a 60-second recording capability, as well as the ability to measure 30 or 45 minutes. It also includes a sub-second function. It is worth noting that due to minor variations and the interchangeability of parts, some series were produced with components from different calibres.