Chinese Abacus
"An Abacus consists of a rectangular frame carrying a number of rods or wires. A transverse bar (centre bar) divides each of these rods into two unequal portions. On the upper smaller portion of each rod are two beads and on the lower portion five beads. The whole acts as a numerical register, each rod representing a decimal order as in our 'arabic' notation."
Source: Gerold Beckers, "Mechanical calculators."

X-Number World