Roman Hand Abacus

(right most column eighths and Modern Roman Numerals on abacus)


References: Roman Abacus, Roman unts of measurement. Brass early reproduction", and Early depiction from "Opera historic et philolgica, sacra et profana".
Note: Eighths can easily be represented on right side by combining by treating the three bottom beads as eighths and top bead as half.
JavaScript Source: abacus.js.