Tair-3 
tele lens for SLR, #661212
300 mm, 1:4.5, M42 mount, 
Zagorsky Optical Mechanical plant (ZOMZ), Zagorsk, USSR
with front cap
lens has inscription "Grand Prix Brussels 1958"

Good condition. Inside there is microdust. Second glass has 2 fungus dots and air bubbles Body has signs of age and dirt. Aperture ring rotates tightly and has a backlash, focus ring rotates properly. Cap is original but does not fixed properly.

This is a USSR telelens which was produced since 1953 till 2005 in USSR (Russia) at three plants: KMZ, KOMZ, ZOMZ with many possible variants.

This is the medium variant of this lens with M42 mount. 
Lens has a one-layered anti-reflection coating. Versions with multi-layered anti-reflection coating have letters "MC" in the name.

In 1958 at Brussels World's Fair (Expo-58) set of Soviet lenses (including MP-2 Russar, Mir-1, Tair-11, Tair-3, MTO-500, MTO-1000) got a "Grand Prix".

Lens is metall and glass, no plastic. So it is very large and heavy. This is a fix telephoto lens, not 55-300 or 80-400. Aperture ratio is 4.5 and lens works throughout the whole aperture scale.

Diaphragm has 16 blades and it is ideally round. It can be set smoothly, not discrete. The quality of the picture is brilliant. 
Lens has a tripod socket 3/8".
Variants:
Tair-3a was produced at ZOMZ with changeable adapter for M42 mount.
Tair-3C and Tair-3FC were default lens for "Photosniper" set. 
Tair-3T is known as a TV lens (produced by KMZ).

Also Tair-3 was made for medium format and got the name "Tair-33". Lens was produced with B or V bayonets.
 
Characteristics:
Lens s/number - 000392
Number of lenses - 3 in three groups.
Angle of view - 8o
Number of aperture blades - 16
Limit of aperturing - 1:4.5 (max), 1:22 (min)
Resolving power - (centre/edge) 45/38 lines/mm
Minimal distance of focusing - 3 m
Type of thread - M42
Type of thread for the nozzles -  72 mm 
Dimensions (mm): 256*88*88
Focal distance - 299,89 mm.
Mass - 1342 g (1387 with cap)