First let me say DO NOT do this to valuable coins, this is for common date coins. A lot of people know about using vinegar and salt and has been around for years. I found out about this many years ago and works very well for removing the crud and the red color on dug nickels. It will usually bring back the date and detail on dateless Buffalo's but it leaves the coin a dull gray color. If you try to remove the dullness it will also remove the date and detail of the coin.