Industar-61L/Z, Soviet lens for SLR camera
50 mm, 1:2.8, M42, #702036
Lytkarinsky Plant of Optical Glass (LZOS), Lytkarino, USSR

Perfect condition.Lens is clear and clean, without any scratches or fungus. Inside there are microspecks of microdust. Aperture rings rotates properly. Focus ring rotates properly and has a very small backlash. Body has signs of age and use. Aperture blades have a bit oil.

I took test photo with this lens mounted via adapter to DSLR "Sony A-100". Test photo is the last.

Camera "Zenit B" is not included and shown as an example of mount.

This is probably the most popular lens from vast "Industar" family. I-61 is a lens with medium lens speed and multilayered anti-reflection coating. Extraheavy lanthanum crown glass "STK-6" is used. Authors of the lens - USSR academician G.Slusarev and V.Sokolova. Optical resolution of this four-lenses system is equal to six-lenses "Helios-81".

This lens was made for rangefinder "FED" and SLR "Zenit" in 1971-90 at three plants: KMZ (Krasnogorsk), FED (Kharkiv), LZOS (Lytkarino) in many different variants.

The lens offered is for SLR camera with M42 mount. Aperture blades are darkened. Hole has a famous "star" which allows to get a typical bokeh for that lens. Used very often for macro.
Lens is very sharp, it's nickname is "Eagle eye". 
This lens was produced with multilayered anti-reflection coating (letters "MC" in the name) or without. 
For cropped Nikon it will have focal distance 75mm, for cropped Canon 80mm.

Lens s/number - 702036
Number of lenses - 4 in three groups, Tessar
Angle of view - 40o 
Number of aperture blades - 6
Limit of aperturing - 1:2.8 (max), 1:16 (min)
Resolving power - (centre/edge) 42/30 lines/mm
Minimal distance of focusing - 0.3 m
Type of thread - M42x1/45,5 mount
Type of thread for the nozzles - 49 mm 
Dimensions (mm): 59*57*57
Focal distance - 52,42 mm.
Mass - 215 g