The Zenith 1731 is an open face mechanical watch movement with a pin-lever escapement featuring ruby pins. It incorporates a ratchet on the dial side and a hidden crown mechanism with a rocker bar. The movement is built on a two-layer base plate, with the back side painted in a golden color. Notable functions of the calibre include stem winding and setting, as well as a sub-second display. The 146B/15 was produced around the period of 1960. Any differences between the 146B/15 and the 146C/15 are unknown.