Its the Rokkor 50 f/1.4 PG. I didnt buy it, I have had it since 1973.I had fungus in a Minolta macro 50/3.5 and I contacted a repair shop. They told me that a lens doesn't get any better by disassembling it and that the fungus may have damaged lens elements permanently, so that removing doesn't restore the lens in a pristine condition.
The repair of the lens would easily exceed its value of about € 50 so I decided to leave the fungus alone (it was only a small patch).
So a logical question is: what type of Rokkor lens is it? If it's a cheap one like a 50/1.7 you'd be better off by simply buying another one.