Roman Hand Abacus

(right most column twelfths and ancient Roman Numerals in display)

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Alt Roman Hand Abacus

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


Russian Abacus

Счеты

(Schety)


Georgian Schoty (not to be taken seriously)


Danish School Abacus


Mesoamerican Abacus

(Nepohualtzintzin, similar to Japanese Soroban base 20)

(Abacus base 20 display base 10, anomaly at 360)


Babylonian Watch (proposed by author)


Chinese solid-and-broken-bar system


Base 16 Abacus


ABACUS Guide Book.
Manual for xabacus (similar X program).
Java Source: abacus.zip.