None of the waxes will take the black off... it's a silver oxide coating. I would start with a small bit of your finest abrasive and, using your thumb and a few drops of water, rub it around and see if it will clear the flats. Start on the text-only side. If that is satisfactory then move to the
horse side. If it's too scary you can send it to me and I'll work on it, or exchange it if you prefer. Most of them are not so dark. That was one particular batch that stayed in the Livers of Sulfur tumbler longer than normal.