The IWC 63 12 watch movement is similar to the ETA 717 movement, but with a lower position and an early Incabloc shock device. The exact differences between the Zentra 185 and IWC 63 12 are uncertain. Most samples of the IWC 63 12 movement feature two bridge layouts, as shown in the archive. However, there are also samples with different bridge layouts. The IWC 63 12 movement functions include manual winding, sub-seconds, and Incabloc Shock Protection. It was used during the period of approximately 1935.