Coining (mint)

In minting, coining or coinage is the process of manufacturing coins using a kind of stamping which is now generically known in metalworking as "coining". This process is different from cast coinage, and can be classified in hammered coinage or hammering and milled coinage or milling.

A coin die is one of the two metallic pieces that are used to strike a coin, one per each side of the coin. A die contains an inverse version of the image to be struck on the coin. Striking a coin refers to pressing an image into the blank metal disc, or planchet, and is a term descended from the days when the dies were struck with hammers to deform the metal into the image of the dies.

Modern dies made out of hardened steel are capable of producing many hundreds of thousands of coins before they are retired and defaced.

Prior to the modern era, coin dies were manufactured individually by hand by artisans known as engravers. In demanding times, such as the crisis of the Roman Empire in the 3rd century, dies were still used even when they became very worn or even when they cracked. The die that was on the hammer side, usually the reverse (back), tended to wear out first. The planchets were usually hot prior to striking. On some Roman provincial coins, some believe the tongs used to move the heated planchet left permanent center indentations on the finished coins. Others attribute these marks to surfacing tools used as a part of planchet preparation.

Experimental archeology suggests that a lower die could be expected to last for up to 10,000 strikes depending on the level of wear deemed acceptable. Upper dies seem to have a far greater range of lives with usable lives ranging from just over 100 strikes to nearly 8000 being reported. Combining archaeological evidence with historic records suggests ancient coin producers (in this case the Amphictions at Delphi) could get as many as 47,000 strikes out of an individual die.

...
Wikipedia