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 - Infinity
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 black finish.
(Source: www.fedka.com)