The Henzi Pfaff 421 is a mechanical watch movement that was developed in 1949. It is part of Eterna's first gents automatic-family with a ball-bearing rotor. However, it was quickly replaced by the 1253UT version, which featured a different rotor shape. Throughout its production period, there were various detail modifications made to the movement. These changes included transitioning from a T- to U shock device and introducing a modified calibre, resulting in different variants of the movement. Not all calibres were made in the TC variant, but the known variants are listed. Signatures of UT versions were also changed to UC. Additionally, the movement includes a detached manual wind and incorporates various functions such as automatic winding and a sweep second hand.