The ETA 2660 is an open face calibre watch movement that features a set-lever spring between plates and a Breguet hairspring. It comes with options of a bimetallic screw balance and Reed's regulator. If equipped with 13 jewels, it has cap jewels only on the balance. The differences between the 291 and 1719 models are unknown. The movement functions include stem winding and setting, as well as a sub-second dial. The ETA 2660 movement was commonly used around the period of 1935.