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 black finished design used on the later Zorki-4 and Zorki-4K.
The pictured lens was made in 1970 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.)