Soroban, Japanese, 1975-1978.
© Science Museum / Science & Society Picture Library
A Japanese abacus with coloured plastic beads in a cardboard case. The soroban has 1 bead above the bar and 4 beads below. It is used for calculations in base 10. The soroban was developed from the Chinese abacus which had 2 beads above the bar and 5 below for working in base 16.