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 conditions having been complied with, the seller had to answer for his being the owner, and in addition seller and purchaser had to fulfil every stipulation specially agreed on; the party failing to do so made reparation to the other, just as if he had deprived him of the article in question.
But a purchase only founded an action in the event of its being a transaction for ready money: a purchase on credit neither gave nor took away the right of property, and constituted no ground of action. A loan was negotiated in a similar way; the creditor weighed over to the debtor in presence of witnesses the stipulated quantity of copper under the obligation (-nexum-) of repayment.
In addition to the capital the debtor had to pay interest, which under ordinary circumstances probably amounted to ten per cent per annum.(5) The repayment of the loan took place, when the time came, with similar forms.
5. Viz. for the year of ten months one twelfth part of the capital (-uncia-), which amounts to 8 1/3 per cent for the year of ten, and 10 per cent for the fear of twelve, months.
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Reference address : https://www.ellopos.net/elpenor/rome/1-11-law-justice.asp?pg=12