Author Topic: Fractional coinage and the duodecimal system  (Read 2385 times)

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Offline Victor

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Fractional coinage and the duodecimal system
« on: August 23, 2012, 11:13:38 AM »
Two bronze coins of Constantine have small denominational marks of XII and XVI respectively on their reverses.  The bronze coin, or follis, had a value of 25 to a denarius, but the marks of value on these fractional coins suggest a value not in increments of five adding up to 25, but rather 4, which suggests a value of 24 folles to a denarius. If the value was 25 folles to a denarius, the fractionals would not have had 12 on the reverse but rather 12 1/2, and 16 2/3 instead of 16. It was easier and more convenient to count small change this way, and then convert to 25 units for larger amounts. Diocletian's Edict of Prices also lends support to the theory that Romans used two systems for their monetary system. For small amounts up to 25 DC, the denarii communes is most frequently named as an even number-- 2, 4, 6, 8 etc. Beginning at 25 DC, increments of 5, and more commonly 10, are used.  The parallel use of 24 and 25 is a duodecimal and decimal system like the old English currency.

for more, including sources-

the two coins below-
A.D. 312-313
PACI PERPET (XII) Pax standing left, holding standard.
RIC VI Rome 355-358

A.D. 312-313
VIRT EXERCIT GALL (XVI) Virtus leaning on a spear.
RIC VI Rome 359-360