COIN. — A piece of metal of a fixed weight, generally round in shape, bearing on its two faces—or more rarely on only one—a representation and an inscription, or only one of these. The obverse of a coin is the face that displays the principal or most interesting type from a historical, archaeological, or artistic point of view; the reverse is the face that shows elements of secondary importance relative to the principal type.
The invention of the coin cannot be placed exactly in time or space, but should rather be considered the result of the slow evolution of the metallic medium of exchange, an evolution driven by the expansion and increasing complexity of commercial relations, culminating in the innovation by which the State monopolized the issuance of coins, simultaneously fixing and guaranteeing their type, metallic alloy, and weight. In the West, this final stage of development took place in the 7th century B.C. within the Greek world. By the mid-4th century B.C., Rome also began issuing its own coinage.
As in modern times, the metals used for coinage in antiquity—with few exceptions—were gold, silver, and bronze. Gold was the foundation of the monetary system of the Eastern world (Lydia, Persia) first, then of the great Hellenistic monarchies (Macedonia, Syria, Egypt), and finally of the Roman and Byzantine Empires. It was always nearly pure, both among the Greeks and the Romans, up to the Byzantine period. Silver, on the other hand, was the basis of coinage among the Greeks, constituting for several centuries their sole minted metal, and among the Romans of the Republic, who struck it in great abundance alongside bronze. The latter was the true coin of the Italic peoples and played a major role in Roman coinage as well, where it constituted Rome’s sole currency before the introduction of silver coinage and always represented a predominant part of circulation, even in the imperial age.
The methods of coin production adopted in antiquity were two: striking and casting. In the former, more frequently used method, a smooth metal disc was struck between two dies bearing in intaglio the type to be impressed on one or both faces. In the latter, molten metal was poured into a recessed mold of the piece to be minted, so that both the disc and the impression on both faces were produced simultaneously. Naturally, the process of die production was far more complex than it is today, and the technical skill and artistic ability of the engraver were of greater value. A phenomenon frequently encountered in antiquity—and not uncommon in the modern era—is the official debasement of the coin’s alloy. This occurred only with silver, as gold always retained its purity. Alongside the debasement of the alloy, another form of monetary fraud was the striking of “fourrée” coins, i.e., coins composed of a core of base metal, generally copper, covered with a thin film of silver. This method was adopted several times in antiquity, as evidenced by surviving coins and literary sources.