The Marvin 540S 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 Marvin 540S are uncertain. Most samples of the Marvin 540S movement feature two bridge layouts, as shown in the archive. However, there are also samples with different bridge layouts. The Marvin 540S movement functions include manual winding, sub-seconds, and Incabloc Shock Protection. It was used during the period of approximately 1935.