This lens belongs to the first series of Industar-22.
Inspired by the 3,5/50mm FED Industar-10, perhaps even with common parts, but with the new diaphragm scale.
Formula: 4 elements in 3 groups
Weight: 117g (front aluminium)
Aperture markings: from 3,5 to 16
Signs: marked 50mm"." / small focus button / small aperture button
Photo 1: Serial number 11558 (Jacques M. coll.).
This lens was mounted on a Fed-Zorki 1948.