Vintage Lens "Industar-61 L\Z" 2.8/50 mm M42 lanthanum glass

Vintage Lens (1980s) "Industar-61 L\Z" 2.8/50 mm lanthanum glass, M42 mount, very good condition.

From the first owner. The fully mechanical lens is based on the Tessar optical design (nicknamed “eagle eye” for its sharpness). Assembly of an optical-mechanical plant in Krasnogorsk.
The main feature of Industar is the diaphragm, which creates an interesting “bokeh”. The diaphragm changes shape and pattern in the blur zone. Its 6 petals on open F2.8 and closed F16 form a smooth round hole. But at F4 it is a hexagon. And on F5.6 and more there is an asterisk (please see the attached photo).
Absolutely working, but there are abrasions in the thread area. Has not been disassembled or repaired. The glass is clean, the multi-coating is intact, without dust, scratches or abrasions.

Includes: lens, front and rear caps, filter Y-1.4x diameter 49, case with screw-on lid.