Zenit's mass-produced Soviet M42 SLR — the E, selenium meter, fully mechanical, 1965.
The Zenit-E is a 35mm film SLR made in the Soviet Union by KMZ (and later BelOMO), one of the most-produced SLRs in history with many millions built from the mid-1960s over a long production run. It was a low-cost, simple SLR exported heavily to the UK and elsewhere, often bundled with a Helios lens, and became a familiar budget entry into film photography.
It is an M42 screw-mount SLR (early examples used the earlier 39mm thread) with a horizontal-travel cloth focal-plane shutter offering a limited speed range, typically around 1/30 to 1/500 plus B. The Zenit-E has an uncoupled selenium-cell exposure meter that needs no battery; the photographer reads it and transfers the values manually. Exposure is fully manual and the shutter is entirely mechanical, working without any battery.
The Zenit-E suits students, beginners and users wanting a cheap, battery-free mechanical SLR to learn on, and it is heavy and simply built. The limited shutter range and lack of automation restrict fast or low-light work, and there is no instant-return mirror on many examples, so the finder blacks out until the film is wound; these quirks are part of its basic character.
On the used market, Soviet build quality varied noticeably between samples, so test each body individually rather than assuming consistency. Check the selenium meter still responds, as these cells fade with age, and run the shutter across its speeds watching for capping and inaccurate timing. Inspect any light seals and dampers for perishing, check the prism and screen, and test the film advance and rewind; expect sample-to-sample variance and inspect carefully before buying.