Originally posted by hangu I would avoid using water. I usually use rubbing alcohol and a soft cloth of q tip since it immediately evaporates and doesn't leave much of a residue.
The soviet era lenses are probably better off with a milder cleanser.
+1 and I might add look for a good quality alcohol (like pharmacy quality).
If that does not do it, you might try high quality zipper fluid (which does already do damage to some sorts of plastic, which the alcohol never does).
If that still does not work, it could be either vinegar (transparent and also concentrated) and/or dishwashing agent.
All that stuff has helped me cleaning lenses, including glass. Blank metal surfaces (no surface layer) can also be polished with toothpaste.
I like clean glass and a real rusty outfit, but that's a matter of taste.
Good luck with the cleaningjob,
Georg