Industar-61, lens for rangefinder camera
52 mm, f/2.8, M39 (LTM) mount, s/n 8677782
"FED" plant, Kharkiv, USSR

Good condition. Front glass has cleavages. Inside there is dust. Body has small signs of age, there is a scratch near serial number. Aperture ring rotates properly, focus ring rotates tightly and not uniformly and has a backlash. Filter thread has a dent

Camera "FED-2" 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" since 1971 till 1990 at three plants: KMZ (Krasnogorsk), FED (Kharkiv), LZOS (Lytkarino).

For "FED-3,-4,-5" it was a default lens.

"Industar-61 L/D" has 6 aperture blades; letters "L/D" mean Lanthanum/ for rangefinder. Also there was I-61 L/Z, where "Z" meant - for SLR camera.
"I-61" (without letters) has either 10 or 6 aperture blades.

Characteristics:
Lens s/number - 8677782
Number of lenses - 4 in three groups, Tessar
Angle of view - 46o
Number of aperture blades - 10
Limit of aperturing - 1:2.8 (max), 1:16 (min)
Resolving power - (centre/edge) 45/28 lines/mm
Minimal distance of focusing - 0.42 m
Type of thread - M39x1/28.8 mount
Dimensions (mm): 585959
Focal distance - 52,42 mm.
Weight - 124 g
Multilayered anti-reflection coating