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
Yet there seems from the first to have been a fixed ratio for the relative value of copper and silver (250:1), and with reference to that ratio the copper coinage seems to have been issued; so that, for example, in Rome the large copper piece, the -as-, was equal in value to a scruple (1/288 of a pound) of silver. It is a circumstance historically more remarkable, that coining in Italy most probably originated in Rome, and in fact with the decemvirs, who found in the Solonian legislation a pattern for the regulation of their coinage; and that from Rome it spread over a number of Latin, Etruscan, Umbrian, and east-Italian communities, --a clear proof of the superior position which Rome from the beginning of the fourth century held in Italy.
As all these communities subsisted side by side in formal independence, legally the monetary standard was entirely local, and the territory of every city had its own monetary system. Nevertheless the standards of copper coinage in central and northern Italy may be comprehended in three groups, within which the coins in common intercourse seem to have been treated as homogeneous. These groups are, first, the coins of the cities of Etruria lying north of the Ciminian Forest and those of Umbria; secondly, the coins of Rome and Latium; and lastly, those of the eastern seaboard.
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Reference address : https://www.ellopos.net/elpenor/rome/2-08-law-religion-army-economy-nationality.asp?pg=27