If the scratches are inclused ( into ) the plastic, they will be visible until the area is reduced down to the bottom of the scratches. I have used CD-scratch remover? polisher? ( fluid) on a flat coffee filter and rub the scratched part of the case on it. It reduces the appearance of the scratch and if done right doesn't frost the holder. As what is said above, be careful not to get fluid inside the holder. My Statue of Liberty coins came in a case also and I just popped the lid off ( mine weren't sonically sealed or anything) and put the coin aside while I cleaned the case. Strangely enough mine were scratched also, but I got them from a dealer and not the mint. Do not use Acetone !! Jim
Don't try this. The PVC primer is intended to actually melt the plastic. And again, remember that there are numerous types of plastics on the market and what may work on one may not work at all on others. Regardless of what you attempt, try it first on a part of the slab that is not very visable.