The Making of Ancient Coins
Until the Renaissance, the process of making coins involved striking a die with hammer to stamp the images onto the faces of the coin. Each coin had to be hand-struck, which led to differences even in coins struck by the same hand and the same die. This has created an abundance of coins to interest collectors, who find that no two coins from the ancient world are ever alike. To understand why that is, it helps to understand exactly how those coins were made.
MAKING THE FLANS
All ancient coins started with blank discs of metal, called flans. The metal varied with the type and denomination of coin that was being created. The highest values of coins were often minted of gold, usually approaching 95% purity. Those coins had what is called ‘intrinsic’ value, meaning that the value of the metal used in the coin was approximately equivalent to the value of the coin. Other metals that were often used for higher denominations of coins were electrum—an alloy of gold and silver.
Once the metal had been acquired, it had to be shaped into flans of the correct weight and size. One of three methods was used to do this. In the first, molten metal was poured into two-sided clay moulds and then cooled, resulting in blank discs of the right weight. Skilled craftsmen may have been able to skip the moulds and pour out uniform dollops of molten metal onto a flat surface. The third method, which offers the finest control, would have involved pouring a specified weight of granulated metal into a mould, heating it to the melting point, and then cooling it in the mould.
With copper and bronze coins, other methods may have been employed. While gold and silver blanks would have been poured into individual molds, the baser metals were often molded in trays with channels or grooves between the coin shapes to allow the metal to fill the entire mold. Some were cast in long rods of a specific diameter, then sawed or cut apart into a certain number of flat discs the way that a modern baker cuts cookie dough into cookies. The end result was a flat, round piece of metal, ready to be placed in a die.
PREPARING THE DIE
The die used to strike ancient coins was most often made of metal—most commonly bronze hardened with tin, though iron was used sometimes. The image that was to appear on the coin face was engraved into the die, in reverse—both negative and mirror image. There were two dies used: the first, for the obverse (front) of the coin, was inset into an anvil. The flan was placed on top of this die. The second die, bearing the image for the rear of the coin, was typically engraved into the bottom of a chisel or pyramid-shaped rod. This was centered on the flan, already in place on the obverse die, and then struck with a hammer. The force of the hammer blow would impress the designs from the two dies on the front and back of the flan, creating a coin.
STRIKING THE COIN
While it’s possible for one person to manage the entire process for striking coins alone, most coins were created by teams of three or more people working together. In engravings and listings of workers for the time, it seems that the process in a mint might go like this: One person would bring the flan from the furnace, where it was heating in preparation for being struck, and position it on the die. A second person would hold the upper die in place, while a third wielded the hammer and struck the coin. The final person would remove the struck coin from the mould just in time for person number one to drop another flan into place. Working in this way, they may have made as many as one coin every three seconds. On a busy day in one of the Imperial Roman mints, there would have been several anvils active at once, churning out thousands of coins a day.