@CornerConcerned asks
old holo has scratches and a little gunk. Can I polish it up before sending it in or will that make it worse?
Jeff answers
I'd leave polishing and repair alone. Rubbing, liquids, wax, or trying to flatten damage can harm the surface or count as alteration, which can affect whether a company grades it. Scratches aren't something you can safely wipe away. Sleeve it as it is and get an experienced opinion before doing anything else. A worn original is better than a card damaged further while trying to improve it.
— Jeff, infinitepulls.com