A KMZ Zenit-E Prototype SLR Camera, chrome, serial no. 64000006, with Industar-50 f/3.5 50mm lens, chrome, serial no. 6346308, body, VG, shutter working, lens, VG, some cleaning marks; This is a prototype of a Zenit-E camera, based upon the Zenit-3M. It is identical to the 3M with the exception of the selenium light meter, instant return mirror and engraving of ‘Zenit E’ to the prism. Both features appeared on the Zenit-E. Also to note, strap lugs are horizontal compared with vertical on previous production models.

The photocell frame is clearly of the type further used on Zenit4, 5, and 6 and thegalvanometer and exposure calculator the same used on later Zenit E, EM, ET, and 11. The mirror oscilating mechanics is the same previusly employed on Kristall 2M and further angular Zenit E cameras.

From The Sales Room lot 1222 3 nov 2016

Another camera with the same features was the Zenit 3EM (#64027660) documented by Alexander Schulz in his book "Zenit" (2003, Lindemanns):

http://www.g-st.ch/privat/kameras/zenitbuchtext.html#71