The lens was independently transferred from the bayonet mount to the M-42 SLR DSLR Mirrorless threaded mount

diaphragm is fully open

I don’t know how well it works, no complaints

Vintage Lens Industar-61  f2.8/53mm ZEBRA M42 Mount Camera and multi-coating for 35 mm SLR cameras

SLR cameras with M42 mount: Zenit, Praktika, Pentax and others

Condition: The aperture ring is difficult to turn, but it can still be adjusted if you apply some effort