The Peseux 123 watch movement is an open face calibre with a pin-lever escapement. It features a coarse imitation of balance screws and an early two-section regulator for coarse and fine adjustment. The movement includes a ratchet under the base plate and a crown mechanism with a rocker bar. It was previously designated as 13-43, but the new designation is 43. The movement functions include stem winding and pin setting, as well as a sub second display. The Peseux 123 was commonly used around the period of approximately 1920.