Have you tried anything yet ? That's why I don't trust these holders for extended amount of time . I prefer the "slab Style" better . Was this in fact in this holder since 1981 ?
No. I don't think that acetone will help. If this was a really valuable coin, I would try a bath in acetone first and a dip second. I don't call those milk spots but some may.
That is a haze on the coin. It is the beginning stage of toning. MS70 will remove it, but make sure that you do a thorough rinse of the MS70.
Coin holders offer varying degrees of protection. But none are 100% including slabs. Coins in holders also need to be stored in environmentally controlled conditions. That means a reasonably stable temperature. And that means in some sort of container with a desiccant. The more humid your environment the more important this is.
I don't feel toning is a minus. I have a few deep golden rainbow toners, and I would never get rid of them. They are unique art.
Based on the discoloring on the 2 x 2 cardboard it looks like the coin wasn't stored properly. Spots and stains on the cardboard are definite signs of mishandling. I've seen this before at coin shows when dealers have multiple binders of coins in 2 x 2's. At the end of the show those binders are tossed in a box and put away for the next show. Stored in a cellar, garage or car trunk waiting for the next event. You the owner could also be at fault. You could be storing your coin in a humid environment or dirty environment. Cellars or attics are the worst places to store coins. Keep in mind a finished basement is still a cellar if the humidity isn't controlled. As far as the coin goes, it's damaged. You may be able to "restore it" with a quick dip but, make sure you use clean dip. This coin is not silver so you don't want to use a dip you used on silver before. There would be traces of silver left behind from prior dipping. The same can be said it the dip was used on copper. If you do dip the coin you need to rinse it well. It may come back to being acceptable but, if the spotting has been on the coin for a long time it will have etched into the surface which means the spotting will return. I don't have a problem with that type of holder I've seen coins that have been stored in them for 50 years without any problems but, it really comes down to storage environment.
Don't know why that one done that ,have it side by side with other,s that are fine, pin hole maybe don't know I personally didn't do that particular 2x2, kind of heart sick about it ,I have few proof Lincoln,s I bought from the same dealer 8to 9 years back!
Not an uncirculated coin, it's a proof coin. At least PR60, possibly higher. Worth a dip in eZest. These holders hold the coin between two sheets of polyester (PET), so no harm from that.
Do you have at least 12 other coins in Flips that have Haze (for Proofs) or blotchy/dark toning (for Business strikes) that is unattractive? If yes, and you would want them "Preserved" (technically professional cleaning), graded, and encapsulated, then I would recommend that you wait for the next ANACS Special for 12 Coins @ $119 (return UPS Shipping & Insurance included); each additional coin for grading is just $10 each. The 12 coins (actually up to 20 coins) will be "Preserved" for an additional $39 Flat fee. This Fee is significantly less than PCGS or NGC charges!