I do not recommend polishing them, but if you must, a quick dip in eZest coin cleaner and a rinse in 100% pure acetone is what I would do. But I would really just leave it as is. John1
I advise against sending it in to be slabbed, it would be a waste of money. But if you do ANACS will cost the least. Please post a full slab photo front and back when you get it back. John1