I've thought about your 1983
Kennedy half dollar w/lucite problem. I see what you're looking at, in front of John's mouth (small die chip). I have a 2023-P Bessie Coleman .25 piece I thought had a large
Cud on her left cheek. I found out otherwise. Usually,
Cuds are found around the rims of coins. The die crack, on my coin, may have exuded base metal from below, forming this error. The 10 ton squeeze, during the minting process, causes the metal or clad layers, to be " molten " immediately upon being struck. As for the "Lucite", I came up with a " Freeze solution ". When most anything freezes, it expands. Freeze the block of lucite for 1-2 days. Then place the lucite block, w/coin, on a hard surface and use a hammer, very carefully. A short crisp rap around the edge should shatter the Lucite. After it shatters and leaves the coin free of permanent encapsulation, you can then determine how to proceed from there. Remember, the metals used in your coin expand and contract as well. Take care !
This is just a theory based on Physics and should not be thought of as a tried and true method.