My experience was the same. I have a variety of 1971 to 1973 Prestige sets that were never removed from the case, stored away for decades. When I recently took a good look at them, I was utterly aghast at what I saw was happening. At some point in time I think someone had checked out the 25c of the set looking for a LB which caused the seal of the plastic overlay to break. Then over the years a chemical reaction of parts of the glued red felt backing resulted in it becoming almost gooey, similar to the early stages of PCV breaddown. I ended up soaking the 25c and 1c in acetone but the finish on the obverse is ruined. I immediately opened the other 1971 - 1972 sets. Thankfully the red felt had only deteriorated into loose fluff easily removed by a quick wash in distiller water, not gooey.






































