This lens is a copy of a Zeiss Sonnar 50/1.5. It was initially made for the Kiev line in Contax/Kiev bayonet mount and later produced in Leica thread mount.

Focal length: 52.4 mm
Aperture: 1:1.5 (steps from 1.5 to 22)
Focusing: 1 m - ¥
Filter size: M40.5x0.5 mm
Optical registration (back focus) :28.8± 0.02 mm
Mount: M39x1 mm (LTM). The lens mounts and RF couples with any Leica or Leica copy (FED, Zorki etc.)

The glass is coated, the barrel has a chrome finish.
(Source: www.fedka.com)