Zorki-3 is a 35mm film rangefinder camera made by KMZ and produced between 1951-56.
This is the first major revision of the basic Zorki 1 body by KMZ with quantity 87.569 units (both with Zorki-3M). It is the first Zorki camera which has combined the rangefinder and viewfinder in one eyepiece.
There are 6 types and 8 sub-types of the Zorki-3
   
Lens: Jupiter-8 50mm f/2.0
Mount: M39 screw mount
viewfinder and rangefinder window Shutter: focal-plane double cloth shutter, horizontaly moving
High speeds: 1/25-1/1000 +B, setting dial on the top plate
Slow speeds of 1, 1/2, 1/5, 1/10 +T (D), setting by a separate knob on the front of the camera  Back cover: Removable back similar to the
Contax/ Kiev bodies
Diopter adjustment Strap lugs
↑ Typing is as to Alexander Komarov
in Fotoua You can also find serial numbers for dating of the cameras in this site.
↑ There is another former USSR cameras classification and info
in SovietCams by Aidas Pikiotas
↑ There are usefull books about cameras of former USSR and have classifications also.
↑ Pages from the the book of former USSR cameras by
Suglob, Shaternik, Kochergin
↑ Discussion about clasifications in the books of Princelle and Suglob, Shaternik, Kochergin in
USSR Photo Forum
↑ You need to set the slow speeds dial on 1/25 for taking pictures with shutter speeds from 1/25-1/1000 and "B" (otherwise you can broke mechanism of slow shutter speeds).