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
We find, for instance, that the forms -"/\/\/", -"P",(14) and -"SIGMA" were not unknown to the Romans, but were superseded in common use by the later forms -"/\/\", -"R", and -"S" --a circumstance which can only be explained by supposing that the Latins employed for a considerable period the Greek alphabet as such in writing either their mother-tongue or Greek.
14. The golden bracelet of Praeneste recently brought to light (Mitth. der rom. Inst. 1887), far the oldest of the intelligible monuments of the Latin language and Latin writing, shows the older form of the -"m"; the enigmatic clay vase from the Quirinal (published by Dressel in the Annali dell Instituto, 1880) shows the older form of the -"r".
It is dangerous therefore to draw from the more recent character of the Greek alphabet which we meet with in Rome, as compared with the older character of that brought to Etruria, the inference that writing was practised earlier in Etruria than in Rome.
The powerful impression produced by the acquisition of the treasure of letters on those who received them, and the vividness with which they realized the power that slumbered in those humble signs, are illustrated by a remarkable vase from a sepulchral chamber of Caere built before the invention of the arch, which exhibits the old Greek model alphabet as it came to Etruria, and also an Etruscan syllabarium formed from it, which may be compared to that of Palamedes--evidently a sacred relic of the introduction and acclimatization of alphabetic writing in Etruria.
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Reference address : https://www.ellopos.net/elpenor/rome/1-14-measuring-writing.asp?pg=21