First of all, WheelyGirl, apologies for the total hijacking of your thread.....
B&J Dude: From the reading I've done, the "radioactive" lenses had one or more elements containing certain radioactive elements which enhanced the optical qualities of the glass. Afaik, Minolta made two: If I recall correctly, one was a 58mm, and the other was mine, the MC 28mm f2.5 SI. When new of course, the glass was perfectly clear, but over time as the radioactive elements decayed, they imparted the tint to the glass. The tint is IN the glass, not on it, and this usually only affects one element. From examining the lens, it appears that this element is just behind the diaphragm. It's definitely not a matter of coating.
These lenses were made around or before 1970. Later glass formulations were changed to eliminate this. I've also heard of other lenses, I think the Kodak Aero Ektar from WWII was one, which also have this characteristic. It is said, and Ralph has mentioned, that exposure to UV light removes this tint and "restores" the lens. When the sun finally comes up this year in my part of the world, I'll give this a try. Until then, I've just sent a roll to the lab with several each unfiltered shots and shots using an 82A filter... I'll see how that works out. Although the jury's out until I see the results, I really like this lens so far. It seems to suit my shooting needs and looks nice through the viewfinder, and it's in excellent condition.