The Bettlach 8429-73 watch movement is a manual wind mechanical movement that was in use around the 1950s. It features a pin-lever escapement and an indirect minute hand friction clutch on the barrel. The movement incorporates an innovative design, replacing the setting-lever spring, yoke, and yoke spring with a single simple part. There is limited information available about the differences between the Brac 40 and 91 movements. Additionally, the Bettlach 8429-73 movement includes functions such as a sweep second hand, although further details are not provided.