The Junghans 651.10 watch movement is an early bumper automatic, designed as a modification of the Harwood automatic. It incorporates a Breguet hairspring instead of a flat hairspring, based on the Jules Jurgensen 300486 design. The specific differences between the 1172 and 1173 models are unknown. This movement features an automatic winding system and a sweep seconds function. It was commonly used during the period from 1935 to 1945.