Addiator Arithma
ADDO Mod 16
ADDO-X 331
Brunsviga 13RK
Brunsviga 13ZK
Calculator "Superautomat SASL"
Facit 1004
Facit EK
Mechanical calculator MADAS
Mellita, Model V/16
Monroe Model L200-X
Nisa PK 5
Original Produx Calculator
Remington Rand Adding Machine
Walther DE 100
Walther RM
XxX calculator

The abacus (plural abaci or abacuses), also called a counting frame, is a calculating tool which has been used since ancient times. It was used in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the Arabic numeral system.[1] The exact origin of the abacus has not yet emerged. It consists of rows of movable beads, or similar objects, strung on a wire. They represent digits. One of the two numbers is set up, and the beads are manipulated to perform an operation such as addition, or even a square or cubic root.