“… and that’s all I have to say about that.”
Many old rangefinder lenses that I have purchased cheap were due to haze or fungus on the lens elements. Removal of this stuff is sometimes hit or miss. I’ve had lenses with obvious haze that cleaned up easily with Isopropol Alcohol … and then there was one that I could never get cleaned as it etched the surface of the element/coating.
Lots of cleaners have been suggested … Isopropol Alcohol, Hydrogen Peroxide, Ammonia, Acetone, Bleach, Vinegar and even some harsher Acids have been used.
Luckily I had a couple of lenses that had fungus were the light surface type that were removable. One I could not remove completely, but it ended up very thin that it had a minimal affect on the incoming light to the film … though I did not try the Ponds Cold Cream rub which is noted by many.
As the lens coating is already damaged by either, I have tried using Acetone:Ammonia (others use Hydrogen Peroxide instead of Acetone) mix to attempt the cleaning. You have to work at it numerous times to slowly, and even leaving it to soak for a day or two, to get it removed or at least less damaged … at worst it will remove the coating (if the lens is coated) … but hopefully makes the lens usable.
There are many discussion posts about extreme haze cleaning … the last resort being polishing the lens with a very mild abrasive. Some have reported using toothpaste, silver polish …
So if you are going for those cheap fungus/haze lenses … do expect to lose 1/3 of the time. It will either come off easily or it just won’t come off.
Note: one time I did inquire to how much a lens polish would cost … the element was a doublet to it first has to be separated, then polished, then recoated, then recemented … estimated cost $375.00.