The Ronda 1236-21 is a mechanical watch movement that was developed in 1949. It is part of the first gents automatic-family with a ball-bearing rotor. However, it was quickly replaced by the 1237UT, which features a different rotor shape. Throughout its production period, the 1237T underwent various detail modifications. Furthermore, there were simultaneous changes to the shock device from T to U, as well as modifications to the calibre, resulting in multiple variants. It is unclear if all calibres were produced in the TC variant, so only the known variants are listed. Some signatures of UT versions were even changed to UC. The Ronda 1236-21 movement includes functions such as automatic winding, sweep second, and a date display. It was introduced around 1949 and used during that approximate period. The manual winding of the movement is detached, with further details resembling the 1249UC.