Coins that have dull luster and a grainy sheen to them are almost always dipped, stripping away a layer of metal in the hope that the smoother silver will give a high mint-state appearance. Some dips, if done properly, remove some stains and fingerprints; others, like the coin pictured below, are ruined by the process. These often are sold as rare brilliant or gem uncirculated pieces, with plenty of hype on the flip. Don’t fall for it.
Post Script: This dipped coin was not offered on Proxibid, but on eBay. Click to expand