- Machine Doubling
- Doubling of coin details caused by double-striking during die production. Machine doubling can detected by slight elongation of details characterised by a smooth graduation between the details of each strike.
- Hub Doubling
- Doubling of coin details causing by double-striking during coin production. Hub doubling can be detected by sharp, distinct edges between the details of the strikes.
- Official back-dated restrike of a coin.
- Patrix die
- A die with a relief design. It can be used to produce working dies.