If you're sure it's acrylic and you really want to get it out, remove as much of that acrylic block as you can first, eg with a saw or something that can cut -- don't use impact methods like a hammer or chisel unless you're ok risking possibly severe damage to the coin. At that point you'll need a glass or steel container that you can cover, a quantity of pure acetone about 4-5 times the volume you'd need to submerge the chunk in, adequate ventilation, a proper disposal method for the used acetone, and experience handling chemicals.

Soak the remaining chunk in pure acetone and leave it. (If your setup includes access to a stir plate, I would maybe set it on there on low speed.) Check the acetone and the size of the remaining chunk maybe 1-3x per day. If the acetone appears a bit sludgy, time to change to a fresh portion. Repeat until you only have a coin left and no acrylic. Do one final soak in fresh acetone, then leave it to air dry.