A “planchet” refers to the blank metal used to make coins. Planchet errors typically include clipped planchets that are the wrong shape or thickness, or planchets that were left blank.

Together, the set fetched $40,250 at auction in 2008. A planchet is a coin blank that's the size and metal composition for the coin that will be minted. They start out as plain discs and end up as ...