Industar-50 was a very successful Soviet made lens. It was a standard or optional lens on practically every Zorki camera, from Zorki-C in the mid 50's to Zorki-4K in the mid 70's. The lens was also made in a 39mm and 42mm SLR mount and was installed (standard or option) on every Zenit model as well, from Zenit-C to Zenit-E. It came in different shapes and finishes, from a chrome collapsible Elmar-style lens to a black "flat" Zenit lens. The optical formula was always the same, the lens produced sharp and contasty images.
This type is the newer, rigid barrel design used on the Zorki-4, Zorki-5, Zorki-6 and Mir.
The pictured lens was made in 1959 by KMZ.
Focal length: 52,48mm (I-22 is 51,39mm)
Angle of coverage (35mm film): 45 degrees (I-22 is 46 degrees)
Focusing: 1m - Infinity
Aperture markings: from 3.5 to 16
Formula: 4 elements in 3 groups, Tessar
Optical registration (back focus): 28.8 ±0.02mm
Mount: M39x1mm. The lens mounts and RF couples with any Leica or Leica copy (FED, Zorki etc.)