The Omega 490 watch movement features a bimetallic screw balance and is based on the Venus 60-II base movement. It incorporates a special barrel with Geneva stopwork. Although a fitting Glycine calibre was available, the decision to use the Venus 60-II as a base movement is interesting, possibly due to the existence of an 8.75''' caliber where manual winding remains possible without removing the crown wheel. This movement is an automatic (bumper) movement with no manual wind capability and includes a sub second function. It was commonly used around 1930.