New-To-Me 1974-1978 Proof Sets With Surprises, Good And Not So Good.

Some random seller had a few 70s proof sets listed for $4 each with $3 combined ship so I tossed out $4 bids and won 5 of the sets. This was 100% sight unseen, no pictures, but the sets I won were 1974, 1975, 1976, 1977, and 1978, so if nothing else, I won them for the Ikes.

That being said, one was a very pleasant surprise, two were great (1977 and 1978) and two were not so pleasant -- the 1975 has beautiful rainbow toning on the cent, but the 1974 Ike/Quarter, and 1976 quarter, have some kind of bizarre toning or mildew or damage or .. I don't know what it is, affecting various coins. So I thought I'd post the Ike here and see if anyone had any ideas as to what's going on and if this is toning from the holders or environmental damage from mildew/water/etc.

The 1975: The whole right obverse of Abe is completely rainbow toned and really pretty, but hard to photograph. A definite winner. However, the reverse of the Ike has a hazy golden-gray kind of toning that seems to absorb the luster...?









The 1974: Everything looks mostly decent, but on the reverse, Ike has a huge nasty white-gray-something that is blocking out part of the legend. But when the light hits the area directly below there (south, so to speak) there is a distinct area of sharp rainbow toning. This is the one I'm most curious about -- what could have caused this? I've never seen one "go bad" in the holder like this - haze, yes, but whatever's on there seems to be eating the reverse. The same gray blotchy junk is on the quarter, obverse, to the left side. It doesn't look like any kind of toning I'm used to seeing. Could it actually be on the holder, and not the coins?





Thoughts appreciated.