I found this 2012 D dime in our change jar - the picture shows two other dimes for comparison. It's very shiny, with no visible layering on the rim/edge. Is this 'unclad'?
Missing clad layer would look like copper and only on one side. Here is an example from my collection -
It's more commonly something that companies do, to make "special presentation sets" they can sell on shopping channels or through magazine ads at inflated prices. Collectors have no use for them, because gold-plating a coin counts as "damage" -- you're altering its surface. Someone probably either inherited or got sick of storing one of those sets, and wisely spent the coins from it. They are interesting to find in your change, though, aren't they? Welcome to CoinTalk!