Didrachm

An ancient Greek silver coin denomination with a value of 2 drachms or 1/2 tetradrachm.

Roman Didrachm

Moneta Historical Research by Tom Schroer

The first Roman silver coin was a didrachm of the Phocaic standard, which means it had a theoretical weight of about 7.58 grams, although in practice it was struck between 6.9 and 7.6 grams.  It appeared in the first half of the third century BC, apparently when the Romans realized a need to have a coin accepted in trade with their Italian (and Greek) neighbors.  Previously the Romans had made only "Aes Rude" bronze money, but about the time the didrachm was issued they began the simultaneous bronze issues of "Aes Signatum" and "Aes Grave".  The Phocaic standard was simply the standard which was most prevalent in central Italy at that time.

The didrachm at first bore the head of Mars on the obverse and the head of a horse with the inscription "ROMANO" on the reverse, but that design soon changed and the weight soon began to slowly decline.  About the time of the First Punic War (264-241 BC) the didrachm's weight was decreased to theoretically six scruples (6.82 grams), although as usual it was struck slightly lower at about 6.6 grams.  Shortly before the Second Punic War the didrachm design was changed (235BC ?) to a young Janus (Fons?) head on the obverse and a quadriga (four-horse chariot) on the reverse, although the weight was maintained at the six scruple level.  The coin became known as a "quadrigatus", although it was still properly a didrachm.  The stresses of the Second Punic War drove the struck weight of the "quadrigati" below 5 grams and eventually produced a still lower weight standard for silver with the introduction of the denarius (q.v.) about 211 BC.

The denarius as the successor of the didrachm initially weighed four scruples (4.55 grams or 72 to the Roman pound), and received the mark of value "X" because it was tariffed at 10 asses (see "As").

The didrachm therefore disappeared from the scheme of Roman coinage about 211 BC, but made its re-appearance in Roman coinage in the reign of Caligula (q.v.) when it was issued by the mint of Caesarea in Cappodocia (q.v.) at a weight of about 7.4 grams, or about double the weight of the drachm of that time.  Caesarea continued to issue didrachms for Claudius (q.v.) and Nero (q.v.) at the same weight standard, although all of the issues are very rare today.  Caesarea continued to issue didrachms for about another 100 years, but the issues for Caligula, Claudius, and Nero were the only ones to have Latin legends (the remainder being Greek legends).