Coins With an Improperly Annealed Planchet
An improperly annealed planchet is difficult to stamp coins. The process of annealing the planchet makes the metal softer and stronger, making it easier to stamp coins. This process is commonly done by heating a planchet over an anvil (block of wood or metal used to hold the lower die during striking).
The obverse and reverse faces of a 5-cent planchet may migrate into patches and pure layers. For example, a 1999-D Jefferson 5-cent coin shows the effects of oxygen flooding the annealing oven. This causes the obverse and reverse faces to appear a mixture of nickel and copper. In addition, the obverse face is not pure as a normal nickel-clad coin is.
Nonstandard copper-nickel clad planchets are another category. They are coins struck on a nonstandard stock (e.g., a dime). Only five or six examples have been identified. A typical nickel-clad dime planchet weighs 2.27 grams, so a five-cent coin struck on this type of stock would weigh 3.18 grams. This type of coin has been misdiagnosed as a copper-nickel clad.