After the first two Emperors this coinage was probably current over the whole Empire ; but it never played any large part in the East.
The commission of "tresviri" of the mint continued to exist as late as the 3rd century; but the names of these magistrates cease to appear on the coins before the death of Augustus. They may still have played a part in the senatorial issues; the imperial coinage fell within the range of the chief imperial officer of finance, the "a rationibus," and, under him, were administered by imperial procurators. The actual striking was entrusted to a staff of im perial freedmen and slaves. From an early date the Emperor began to exercise a controlling influence over the bronze token coinage also. The two mints may after a time even have been housed in the same building; at any rate the authority of the senate came to be more and more an empty form.
The Roman Republic had only known gold as an emergency or as a foreign coinage. Augustus from the first made his standard gold piece, the "aureus," the head of his system. The denarius however continued to be struck pure and of unimpaired weight; the coinage rested on a bimetallic basis. The aureus weighed the forty-second part of a pound, the denarius the eighty-fourth; twenty denarii went to the aureus. The token coinage consisted of the sestertius and the dupondius, struck in brass, the fourth and the eighth part of the denarius respectively. The as, the fourth of the sestertius, and the quadrans, the fourth of the as, were struck in copper. Gold and silver were both struck almost pure. Base, plated denarii were not uncommon, but were the work of forgers. Under Caligula and Claudius, however, there is reason to think that the government abandoned its sound principles and condescended to make an unlawful profit by this device itself.
Later Imperial Changes.—Nero reformed the coinage, re ducing the weight of the aureus to the forty-fifth part, that of the denarius to the ninety-sixth part of a pound. More important still, he added ten per cent of alloy to the hitherto pure silver. The relations of the coins to one another remained unchanged. Various more or less respectable motives for this reform have been suggested; and, so far as concerns the reduction of weight, there may have been justification for this measure of inflation.
It is impossible to judge the debasement of the silver so chari tably. It can be nothing but a device of a spendthrift government for meeting its obligations cheaply.
The evil consequences of Nero's debasement were slow to make themselves felt ; but they were nevertheless disastrous. Again and again under stress of circumstances the government resorted to the same expedient. The percentage of alloy in the silver rose to as much as forty per cent under Septimius Severus.
Caracalla took the next step. He reduced the weight of the aureus to a fiftieth part of the pound and issued a new silver coin, the "antoninianus" or double denarius at the weight of about a denarius and a half. In the following period the aureus con tinued to decline in weight and the denarius, after a struggle, suc cumbed to the less honest double piece.
A final debasement of the silver by Gallienus at the crisis of his reign, when Valerian was a Persian captive and the West cut loose under an Emperor of its own, overtaxed the patience of a i long-enduring public. The Antoninianus was no longer taken at its nominal value; confusion reigned and prices rose to absurd heights.
It was Aurelian, the "restorer of the world," who stabilized the coinage. The details of his work are obscure; what is certain is that his stabilization was so unpopular that it led to a riot, on the scale of a miniature civil war in Rome. A coin like the antoninianus was struck, but its value was reduced far below par. Gold was not restored on a reliable basis and the process of inflation began again. Diocletian had no choice but to deal sum marily with this problem, before he could restore a coinage that deserved confidence.
Non-imperial Coinages.—In the West, local coinage in South Italy, Sicily, Gaul, Spain and Africa is found commonly under Augustus and Tiberius and sporadically, down to Galba. When this local coinage ceased, the duty of supplying the whole of the West fell on the mints of Rome, sometimes assisted by branches at Lugdunum (Lyons). In the East the case was very different.