The Cyma Tavannes 420KT watch movement is a gents automatic-family movement that was produced during the period of 1949-1950. One notable feature of this movement is the inclusion of a ball-bearing rotor, which enables smooth automatic winding. The movement underwent modifications during its production, including the change from T- to U shock device and a modified calibre. It should be noted that various variants of the movement exist, with the TC variant being the most known. Some calibres may have also been produced in the UT variant, although specific details are not provided. The movement also features a detached manual wind function and includes a sweep second hand.