It is possible for a modern coin to be missing the clad, or nickel, layer from both sides, but it is uncommon. In this case, the copper portion, which makes up 90 percent of a coin, is exposed. Usually, coins missing clad layers are identified before leaving the mint.
A coin with a clad error is potentially worth hundreds of dollars. Top specimens are bright and shiny and do not appear as if they have been circulated. In addition, the type of error is important. Some coins are missing just part of the clad layer, some are missing one full side, and others have no layers at all. The more clad that is missing, the more valuable the coin is.