Mechanics: A-
Focus - I took the lens apart, cleaned and re-greased the focus helixes with
Nyogel 744 grease (it won't travel to the iris blades), now it's easy and
smooth to rotate from close-point to infinity. Because of the history of the
lens, even with the new grease it has a little friction and not total silent
when changing focus, but still better than most used lenses on the market.
Back focus is calibrated on a Canon 5D MkII with a Pentacon-to-EOS adapter,
meaning the distance marks on the lens reflect the actual distance
of the focus plane from the sensor (you get perfect infinity at the end of
rotation). The adapter is included in the auction, I recommend you not to
take it off (other adapters might have slightly different thickness and
change flange distance).
Iris - I de-clicked and re-greased the aperture ring, it works smoothly,
the iris blades are clean, aperture works all the way from f2.8 to f22.