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
The old Servian
arrangement for voting in the centuriate comitia, under which the
first class, with an estate of 100,000 sesterces (1000 pounds) or
upwards, alone possessed almost half of the votes, again took the
place of the arrangements introduced in 513 to mitigate the
preponderance of the first class.(25)
Practically there was thus
introduced for the election of consuls, praetors, and censors, a
census which really excluded the non-wealthy from exercising the
suffrage. The legislative initiative in the case of the tribunes
of the people was restricted by the rule, that every proposal had
henceforth to be submitted by them in the first instance to
the senate and could only come before the people in the event
of the senate approving it.
These enactments which were called forth by the Sulpician attempt at
revolution from the man who then came forward as the shield and sword
of the constitutional party--the consul Sulla--bear an altogether
peculiar character.