The Cyma Tavannes 940 mechanical watch movement features a unique crown mechanism with a rocker bar, occasionally accompanied by a ratchet wheel on the back side. Various versions of the movement exist, some incorporating a click on the dial side and others including a functionless crown wheel. The exact correspondence between these variations and the numbers 1237, 1238, 1245, 1249, 1269 remains uncertain, although the AS 1245 is known to possess a ratchet wheel on its reverse side. This movement offers manual winding, sub-second functionality, bascule winding, and was predominantly employed around the 1950s.