Goldpick
Chris Johnson
SA Bogan and Paulmarr use electrolysis on their silvers considering the original state of most coins they find. You will have to keep an eye on the coin to ensure you don't go too far with the electrolysis, as the black coating comes off pretty quick in most cases. Slipped disc's method might be a bit less aggressive on the coins, just enough to loosen the black coating before giving a gentle rub with some more bicarb to remove the remainder..