The Zenit 3M and the Zorki 6 (shown previously) were based on the Zorki 5 body but with a hinged back. The Zenit 3M was identical the Kristall produced fin 1961 and 1962 with the exception of the top plate. The Kristall had a cast metal plate and the Zenit 3M had a stamped plate. The Zenit 3M was produced from 1962 to 1970.
This well worn example was made in 1966. The Zenit 3M like all previous KMZ SLRs used a M39 mount lense with the same lense registration as the M42 "Pentax" mount. Thus a cross between the Pentax and Leica lens mounts.