Coin Curiosity

Researching the history coins of the British Commonwealth

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Numismatic terms

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.
The thin layer of oxidation on the surface of a coin; sometimes used to describe the toning.
Patrix die
A die with a relief design. It can be used to produce working dies.