This is something I posted on a different board and thought I would share it here. I know many here don't care for the use of acetone but it can be helpful on some coins. The sad part is what you might find under the PVC.
This is not something the young folks should be messing with.
There are safe ways to use acetone but it can hurt you if not done correctly.

Before pics.

These are after one acetone bath and after two baths. No rubbing.

This is after several acetone baths. No rubbing. Not real pretty.
Lots of marks under the PVC.