Roman Hand Abacus
right most column twelfths and ancient Roman Numerals in display
Alt Roman Hand Abacus
right most column eighths and modern Roman Numerals on abacus
Russian Schoty
Georgian Schoty (not to be taken seriously)
Danish School Abacus
Mesoamerican Nepohualtzintzin (similar to Japanese Soroban base 20 (except at X))
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.