The Certina 15-20 watch movement, used from 1966 to 1970, features an indirectly driven minute and automatic gear integrated into the movement, allowing for a low-profile design. It includes a ratchet on the dial side and a crown mechanism with a rocker bar. The smaller rotor employs a ball bearing. Detailed differences between the Movado 387 and 389 are currently unknown. The movement offers functions such as automatic winding, sweep seconds, and a quickset date function.