Industar-26m, 
silver lens for rangefinder, #1792004
50 mm, f/2.8, M39 (LTM) mount lens, 
"FED" plant, Kharkiv, USSR

Very good condition. Glass has tiny cleaning microscratches. Inside there are microspecks of microdust and a dot (maybe dirt, maybe fungus, I can't define). Aperture ring rotates properly and has a backlash. Focus ring rotates a bit not uniformly and has a backlash. Body has signs of age. Filter carving is damaged.

Camera "FED-2" is not included and shown as an example of mount.

This is a normal lens with anti-reflection coating for rangefinders. Lens was default for camera "FED". It is the only version of this lens (with the letter "M"). Simple "Industar-26" remained experimental.
Lens was produced since 1954 for M39 mount at "FED" plant in Kharkiv. Also a small lot of this lens for SLR camera was made at KMZ (Krasnogorsk). Variant for enlarger was known as "Industar-26M-U". 

Characteristics: 
Lens s/number - 1792004
Number of lenses - 4 in three groups, Tessar
Angle of view - 45o 
Number of aperture blades - 10
Limit of aperturing - 1:2.8 (max), 1:22 (min)
Resolving power - (centre/edge) 27/18 lines/mm
Minimal distance of focusing - 1 m
Type of thread -M39х1/28,8 (Leica screw mount)
Type of filter thread - 40.5x0.5 mm
Dimensions (mm): 55*57*44
Focal distance - 52,49 mm.
Mass - 114 g
One-layered anti-reflection coating