This reflex unit, serial number: 634115 is fitted to a Zorki-4 body, serial number: 63193225. There is another number on the front of the top-plate, behind the reflex housing: 633024. Many features of the Zorki-4 are retained, except for the self-timer and flash synchronisation. The original focal plane shutter, with speeds from 1 sec to 1/1000 sec + B remains. The mirror is flipped into position by the lever at the back of the reflex housing, near the top of the camera. The shutter is fired by the trigger below the reflex housing. The original shutter release of the Zorki-4 is replaced by a rotating button for disengaging the sprockets for film rewinding. The serial numbers suggest that this unit was assembled by KMZ in 1963.