Striking, not stamping by machine
Ancient Greek and Roman coins were made by hand. The standard method, called striking, used a pair of engraved metal dies and a hammer. There was no press in the modern sense for most of antiquity, which is one reason that no two ancient coins are exactly alike. This process is central to coin minting as a craft.
Not every ancient coin was struck, however. Early Chinese coins, for instance, were cast in moulds, and early Roman bronze pieces known as aes grave were also cast. This article focuses on the struck coinage of the Greek, Persian, Hellenistic and Roman worlds.
Preparing the metal
The first step was making the blank, usually called a flan. Metal was refined and alloyed to the desired purity, then melted and poured into small moulds or onto a flat surface, producing discs or lumps of roughly the intended weight. In many mints the flans were then heated, so that the metal was soft enough to take the die impression cleanly. The weight needed to be close to the standard, and mints often accepted small variation.
Purity mattered because the value of a coin rested on its metal. Lydian and Persian coinage, for example, was known for good gold and silver, and Lydian gold coinage helped make that reputation. Skilled assayers and officials tested the metal, though ancient methods of testing could not detect small differences easily.
The dies
Two dies were used. The lower die, often called the anvil die, was set into a block or an anvil, and it usually carried the obverse design. The upper die, sometimes called the punch or hammer die, was held by hand above the blank and carried the reverse design. Dies were typically made of bronze or iron and were engraved in reverse, so that the coin would show the design the right way round. Engravers worked with small tools, and their skill varied. Some Greek coins of Sicily and southern Italy, for example, are widely admired as small works of art.
Dies wore out or broke. The upper die suffered more because it took the hammer blow, so mints had to make many new ones. Numismatists, who study coins, can match coins struck from the same die by tiny flaws, and from the number of dies they sometimes estimate how large an issue was, although such calculations are uncertain.
The strike
To make a coin, a worker placed the heated flan on the lower die, set the upper die on top, and a second worker struck the upper die with a heavy hammer. A single blow, or a couple, drove the metal into the engraved hollows of both dies at once. The coin was then removed and the process repeated. Off-centre strikes, double strikes and cracked edges are common and show how quickly the work went.
Early Greek coins often had a simple punch mark or an incuse square on one side, produced by the punch. Later issues carried designs on both sides. Roman mints produced very large numbers of coins in this way, with teams working in organised workshops. The Roman moneyers of the Republic were officials who often put their names or family emblems on coins.
What the designs said
Coin designs were more than decoration. Greek cities used badges that identified them: the owl of Athens, the turtle of Aegina, the winged horse of Corinth. Because the owl stood for Athens and its goddess, Athenian coins were easily recognised across the Mediterranean, a point that ties in with the Laurion silver mines.
In the Hellenistic period, kings placed their own portraits on coins, a practice that Roman rulers carried much further. Roman coins carried the emperor’s portrait, titles and messages about victories, buildings, peace and the imperial family. Because coins moved through the whole empire and were handled by many people, they were an effective way to circulate an image of the ruler. After the Augustan principate began, such portraiture became a regular method of imperial communication. Historians still debate how far ordinary users read the messages, and how much was decided by the emperor himself rather than by mint officials.
Inscriptions, mint marks and control marks also record where a coin was made and sometimes by whom. These details help modern researchers date issues and trace military and political events.
Later developments and limits
Over time, techniques changed. Edges were sometimes shaped or marked, and in the Roman world many silver coins gradually lost purity as emperors faced financial strain, a process that is documented from the first century CE and became severe in the third century.
Because the process was manual, many coins show small imperfections, and counterfeits and plated pieces existed alongside official ones. These facts do not make ancient coinage less impressive. They mean that each coin is the product of hands, tools and decisions, which is why museums and collectors study even worn examples.