After dismantle of Soviet Union, trying to stay on float many camera manufactories start cutting cost of the production by substituting metal parts with plastic. This black Zenit ET is great example of such practice. Made mostly from plastic it still have Leica hard, and Zenit filling.
Cameras were fitted with more then 10 variation of lens:
MS Helios 44-3,
MS Helios 44M-4,
MS Helios 44M-5,
MS Helios 44M-6,
MS Helios 44M-7,
MS Helios 77M-4,
Black Industar 50-4(semi confirmed)
And possibly other lenses.
Probably in such strange and difficult times supply was scarce and whatever lenses and materials BELOMO can find, they used for production of the cameras. As result many modification of the camera existed.
Major difference is that cameras fitted with Helios 44-3 and Industar 50 lens do not have automatic aperture control.
Other differences are in shatter buttons and shatter speed wheels.
Also existed bronze colored Zenit ET and classic chrome cameras, probably made from old stock parts.(see Wiki)