Jupiter-8, 
silver lens for rangefinder camera
50 mm, f/2, M39 (LTM) mount, s/n 6212324
Krasnogorsky Mechanical plant named after Zverev (KMZ), Krasnogorsk, USSR

Very good condition. Lens is clear and clean, without any scratches or fungus. Inside there are microspecks of microdust. Body has signs of age. Aperture ring rotates easily. Focus ring rotates a bit tightly and a bit not uniformly. Both rings have a backlash.

Camera "Zorki-4" is not included and shown as an example of mount.

This is a normal lens with high lens speed and anti-reflection coating for rangefinders. Lens was default for cameras "Kiev", "Zorki", "Leningrad". 
Lens was based on "Carl Zeiss Jena Sonnar" 2/50, which was designed be Ludwig Bertele in 1930-32. After the II World War technology, materials and spare parts were moved to USSR. 
Lens was produced since 1948 for M39 mount and since 1956 for Contax RF mount.

Characteristics: 
Lens s/number - 6212324
Number of lenses - 6 in three groups, Sonnar
Angle of view - 45o 
Number of aperture blades - 9
Limit of aperturing - 1:2 (max), 1:22 (min)
Resolving power - (centre/edge) 39/24 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): 43*50*50
Focal distance - 52,49 mm.
Mass - 124 g
One-layered anti-reflection coating
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