Helios-44-2, black lens for SLR camera
58 mm, f/2, M42 mount, s/n 83300382
"Jupiter" plant, USSR

Very good working condition. Glass is clear and clean, without any fungus or scratches. Inside there are microspecks of microdust. Focus ring rotates properly, aperture ring rotates easily and has a small backlash. Body has small signs of age and use. Aperture blades have oil. Filter carving has a dent.

Camera "Zenit ET" is not included.

I took a test photo with this lens set on DSLR "Sony A-100" via adapter. Test photo is #2.

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 since 1958 till 1994 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.

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

Characteristics: 
Lens s/number - 83300382
Number of lenses - 6 in four groups, Biotar
Angle of view - 40o
Number of aperture blades - 8 
Limit of aperturing - 1:2 (max), 1:16 (min)
Resolving power - (centre/edge) 38/20 lines/mm
Minimal distance of focusing - 0.5 m
Type of thread - M42 mount
Type of thread for the nozzles - 49 mm 
Dimensions (mm): 47*60*60
Focal distance - 58,60 mm.
Mass - 215 g 
One-layered anti-reflection coating