Roman Hand Abacus
(Ivory Abacus from 2nd - 5th Century)
Rails:
References:
Roman Abacus,
Roman unts of measurement.
Brass early reproduction",
Early depiction from "Opera historic et philolgica, sacra et profana", and
Ivory Abacus.
Note: there is an extra space for "MM" not present on other known Roman Abacii
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