The Zenit-E was intoduced in 1965, but this one was produced later. The first types have 39x1 lens thread (in 1968 changed to 42x1 universal mount) and no instant return mirror (introduced in 1967). Over 3 million made.

A very nice internet-page in English about this camera is to be found at:

http://cameras.alfredklomp.com/zenite/index.htm.