Bought this one cheap, going to put it in a holder, what should I do first... Oops...add another choice...eZest dip.
Normally I would say leave them alone as they're Proofs but in this case they're looking really sad and they didn't cost that much! I would start with distilled water then go to acetone then MS70, it's a gamble but a gamble I would take!
I think that I would remove them and put them in a hard plastic set. If the toning furthers to the worst, then I might take different action.
Pretty sure that neither water nor acetone will touch that. Looks like plain old silver sulfide toning. The usual chemical agents will work, but I'm not sure the results would be attractive. Those proof fields really highlight any sort of surface damage.
Sorry, I was thinking of the eZest dip, since the toning does't look really pretty and with or without the original packaging, they are proofs. I think leaving them in the original packing would just invite the toning to go less attractive than it already is. I do have a case for them.
I would put them in better display. Yes, the original would have been nice, but already the original is damaged, and the original is allowing the toning to get worse. As I recall, when these were originally sold there was no claim the holder was good for permanent storage. However, I would leave off the water, acetone, brillo pad, or whatever. The water, and perhaps acetone, might be good if the problem were foreign gunk like fingerprints. But you seem only to have toning, and, as mentioned, removing toning will further damage the proof surfaces.
I would not mess with the cent. It won't turn out well. The silver could be helped with a dip but there is nothing to gain from that. I would put each coin in some type of a new holder, just the way they are.