A piedfort is an unusually thick coin, often exactly twice the normal weight and thickness of other coins of the same diameter and pattern. Piedforts are not normally circulated, and are only struck for presentation purposes by mint officials, or for collectors, dignitaries and other VIPs. Piedfort is less commonly spelled "piefort".

A pattern coin is a coin which has not been approved for release, but produced to evaluate a proposed coin design. They are often off-metal strike, to proof standard or piedforts. Many coin collectors collect and study pattern coins because of their historical importance. Many of the world's most valuable coins are pattern coins; nearly 25 of the pieces listed in 100 Greatest US Coins are pattern coins.