Jupiter-21M, Soviet telelens for SLR camera
200 mm, 1:4, M42, #92001888
Vologodsky Optical Mechanical Plant (VOMZ), Vologda, USSR

Excellent condition. Lens is clear, without fungus or scratches. Inside there are microspecks of microdust. Blades do not have oil. Aperture works properly in both modes ("A-M").

Camera "Zenit B" is not included.

"Jupiter-21M" is USSR fixed manual telelens which It was produced in 1973-1992. This lens has one-layered anti-reflection coating.
Lens has 8 aperture blades. Aperture meaning is changed discrete, not fluently.

Letter "M" means that lens has mode for jumping aperture setting with a special pin and switch mode "A-M", weight and minimal distance of focusing increased comparing with "Jupiter-21" and "Jupiter-21A", number of aperture blades was reduced. In 1980-s when these changes were introduced production was moved from KMZ to VOMZ.

Body is fully metallic. Lens does not like contre-jour and side light, so built-in lens hood is included.
In 1960 lens was rewarded with 1st degree award at Exhibition of Achievements of National Economy.

Variants:
"Jupiter-21" was produced at KMZ, M39 mount
"Jupiter-21A" was produced at KMZ, M42 mount, did not have jumping aperture, another body, letter "A" means that with adapter this lens can be mounted on camera with mounts: M39*1/45.2, bayonet H (Nikon F), bayonet K (Pentax K-mount) and others, weight 740 g, 10 aperture blades
"Jupiter-21T" - for TV cameras
Price for this lens was rather high - 140 Soviet Roubles. Average salary was 120 Soviet Roubles per month.

Lens s/number - 92001888
Number of lenses - 4 in three groups, Sonnar
Angle of view - 12o 
Number of aperture blades - 8
Limit of aperturing - 1:4 (max), 1:22 (min)
Resolving power - (centre/edge) 50/36 lines/mm
Minimal distance of focusing - 1.8 m
Type of thread - M42x1/45,5 mount
Type of thread for the nozzles - M58x0.75 mm 
Dimensions (mm): 78*78*165
Focal distance - 199.78 mm.
Mass - 955 g