Jupiter-8 2/50 black lens for rangefinder camera M39 LSM mount USSR KMZ

Jupiter-8
black lens for rangefinder camera
50 mm, f/2, M39 (LTM) mount, s/n 7405840
Krasnogorsky Mechanical plant named after Zverev (KMZ), Krasnogorsk, USSR
 
Perfect condition. Lens is clear and clean, without any scratches or fungus. Inside there are microspecks of microdust. Body has very small, insignificant signs of age. Aperture and focus rings rotate properly.

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.

haracteristics: 
Lens s/number - 7405840
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 - 120 g
One-layered anti-reflection coating