Plowing through another box, I just found a packet of envelopes from the Philadelphia Mint, containing proof sets from 1958, 1960, 1962 . . . haven't checked all the dates yet.
When I opened the first three, I discovered that some of the coins have black spots. Apparently the packaging wasn't completely inert. Most of the coins are pristine, and I can sell the undamaged coins separately. So far the bad damage seems to be on the silver coins, not the pennies and nickels.
My problem is what to do with the damaged ones. Do these have any value at all to collectors? I don't feel like going through the work of taking pictures and listing them if they're worthless. I can add them to my scrap silver and sell them for the metal content.