Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
But the imperial coinage begins with Caesar. Exactly like Alexander, he marked the foundation of the new monarchy embracing the civilized world by the fact that the only metal forming an universal medium obtained the first place in the coinage. The greatness of the scale on which the new Caesarian gold piece (20 shillings 7 pence according to the present value of the metal) was immediately coined, is shown by the fact that in a single treasure buried seven years after Caesar's death 80,000 of these pieces were found together. It is true that financial speculations may have exercised a collateral influence in this respect.(114)
114. It appears, namely, that in earlier times the claims of the state-creditors payable in silver could not be paid against their will in gold according to its legal ratio to silver; whereas it admits of no doubt, that from Caesar's time the gold piece had to be taken as a valid tender for 100 silver sesterces. This was just at that time the more important, as in consequence of the great quantities of gold put into circulation by Caesar it stood for a time in the currency of trade 25 per cent below the legal ratio.
As to the silver money, the exclusive rule of the Roman -denarius- in all the west, for which the foundation had previously been laid, was finally established by Caesar, when he definitively closed the only Occidental mint that still competed in silver currency with the Roman, that of Massilia. The coining of silver or copper small money was still permitted to a number of Occidental communities; three-quarter -denarii- were struck by some Latin communities of southern Gaul, half -denarii- by several cantons in northern Gaul, copper small coins in various instances even after Caesar's time by communes of the west; but this small money was throughout coined after the Roman standard, and its acceptance moreover was probably obligatory only in local dealings.
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Reference address : https://www.ellopos.net/elpenor/rome/5-11-old-republic-new-monarchy.asp?pg=176