LAST resort though. O_O I don’t wanna drill anything unless absolutely necessary because one small slip and I go through the capsule and into the coin since there’s not much space between them.
If the plastic protrudes above the surface of the coin, I have use a nail trimmer to cut the top of the rim at several places , and that often help to loosen its grip. Yes, obviously ( as someone will quip) be carefully and keep away from the coin. Jim
I once tried to get a Morgan dollar out of a PCGS slab with a circular saw. It worked, except I ended up with two Morgan half dollars.
With the capsule open and the edge of the capsule against a soft cloth on a table, put your thumbs against the top of the capsule and your fingers on the back and do your best to bend or break the capsule. Under no circumstances would I drill anything!!!
Not sure if this is the same situation, but to remove a quarter from a US Mint capsule half, I held the capsule half in a pair of channel lock pliers by the rim - sort of like this but on the capsule half instead of a bare coin: https://www.alamy.com/stock-photo-euro-coin-in-pliers-100083625.html Then used a heat gun on the plastic side of capsule half. I actually only used the pliers because it got too hot while I held the capsule with my fingers. The capsule got very flexible and actually bent backwards as I held onto it, dropping the quarter out as it bent from me holding it. I will note that the capsule had a raised rim edge that seemed to help it bend backwards - it was not the smooth sided half. For my situation the highest probability of damage was from me and the pliers rather than the heat and any melting plastic. My saving grace was that I wasn't squeezing the pliers hard, just holding the capsule. In any case, basically all of this to say that well before it melts it gets a heck of a lot more flexible and you should see the capsule distort, likely dropping the coin out, before you see any melting or stickiness.
I'd try a little heat to try to expand the plastic without expanding the metal. Does the other half of the capsule react to acetone? A little of that might loosen it up.
Not sure I'd try the acetone; it could cement the capsule even more firmly to the coin, and it would also ruin the transparency. I know we aren't trying to preserve the capsule, but as long as the coin's stuck in it, it's nice to be able to see the coin...
You might tap the edge of the holder on a hard surface. Not hard enough to do any damage. This has worked for me.
I insert the point of a utility knife between the edge of the coin and the rim of the capsule. Then gently pry the coin out.
NO…do not dissolve the plastic with acetone. The plastic will adhere to the coin. Do what @Dynoking suggested or get a very small pair of needle-nose pliers and slowly break up the remnant capsule…imo…Spark