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
These distinctions may perhaps have already existed partially in the time of the patrician government, and, so long as families of higher and humbler rank were distinguished within the patriciate, may have served as external insignia for the former; but they certainly only acquired political importance in consequence of the change of constitution in 387, by which the plebeian families that attained the consulate were placed on a footing of equal privilege with the patrician families, all of whom were now probably entitled to carry images of their ancestors.
Moreover, it was now settled that the offices of state to which these hereditary privileges were attached should include neither the lower nor the extraordinary magistracies nor the tribunate of the plebs, but merely the consulship, the praetorship which stood on the same level with it,(7) and the curule aedileship, which bore a part in the administration of public justice and consequently in the exercise of the sovereign powers of the state.(8)
7. Cf. II. III. Praetorship
8. Thus there remained excluded the military tribunate with consular powers (Cf. II. III. Throwing Open of Marriage and of Magistracies) the proconsulship, the quaestorship, the tribunate of the people, and several others. As to the censorship, it does not appear, notwithstanding the curule chair of the censors (Liv. xl. 45; comp, xxvii. 8), to have been reckoned a curule office; for the later period, however, when only a man of consular standing could be made censor, the question has no practical importance. The plebeian aedileship certainly was not reckoned originally one of the curule magistracies (Liv. xxiii. 23); it may, however, have been subsequently included amongst them.
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : http://www.ellopos.net/elpenor/rome/3-11-government-governed.asp?pg=5