MC Helios-44m-5, black lens for SLR camera
58 mm, f/2, M42 mount, s/n 91248069
"Jupiter" plant, Valdai, USSR

Very good condition. Fully working. Lens is clear, without any fungus or scratches. Inside there are microspecks of microdust. Aperture and focus rings rotates properly and fluently. Body has very small signs of age and use.

Lens was tested with DSLR "Sony A-100". Test image is #2.
Camera "Zenit ET" is not included and shown as an example of mount.

This lens was designed at Krasnogorsky Mechanical Plant. This is a representative of vast "Helios-44" family, that was based on German Carz Zeiss Jena Biotar 2/58. Firstly it has a name "BK" - Biotar from Krasnogorsk.

Optical scheme was calculated in 1951 at State Optical Institute. Lens was produced in 1958-94 at three plants: KMZ, BelOMO, Jupiter with four possible mounts: M39, M42, Pentax-K mount, Start. This is one of the most popular lenses in the world.

It is the only lens in the world which was marked after the quality measurement according to its quality (for example, "Helios-44M-4" has the lowest quality, "Helios-44M-7" - the highest). 

This lens has a jumping diaphragm and needs a proper camera to activate the aperture (a pin on the rear side of the lens must be pressed and the aperture will close till the meaning set). Red letter "R" on the body must be put when taking picture on infra-red film. 

When mounted with adapter on Canon, for example, its focal distance will be: 92,8mm (for APS-C), 75,4mm (for APS-H).

Lens s/number - 91248069
Number of lenses - 6 in four groups, Planar
Angle of view - 40o
Number of aperture blades - 6 
Limit of aperturing - 1:2 (max), 1:16 (min)
Resolving power - (centre/edge) 41/20 lines/mm
Minimal distance of focusing - 0.5 m
Type of thread - M42 mount
Type of thread for the nozzles - 52 mm 
Dimensions (mm): 42*64*64
Focal distance - 58,60 mm.
Mass - 234 g 
Muli-layered anti-reflection coating