The ETA 2639 watch movement is a detached manual wind mechanism with an indirectly driven minute hand, enabling the use of a larger balance wheel while maintaining a low profile. It incorporates a Type VS variation, featuring a single-part rotor that is 0.6mm taller than the standard model. The movement offers various functions, including automatic winding, a digital display showing seconds, minutes, and jumping hours, as well as a quick-set date feature activated by repeated crown pulling. Additionally, it includes a sweep seconds hand and a calendar display. The ETA 2639 movement was commonly used during the period of approximately 1975.