“Just in time for school!”
Released in 1960 by Hasbro, Adding Machine was a functional mechanical calculator with some kid-friendly quirks.
With a blue case made of high-impact plastic, the toy was sized (10-inches long by 5 ¾-inches wide) and styled to resemble similar electric models of its time. Kids performed calculations by manipulating five gray sliders, labelled A-E, using built-in finger buttons. The Adding Machine could add to 99,999, as well as multiply and subtract.
Each slider had a set of black and red numbers on it. Black numbers were used for addition while red numbers were used for subtraction.
As a mechanical toy, it took some getting used to. To add, the user selected a number and pulled the corresponding finger button to the bottom. To subtract, the child added negative(red) numbers. Multiplication was also a case of special addition: repeatedly adding numbers to complete the equation.
A built-in register kept track of calculations using a simple direct-carry mechanism. By default, the register was masked from view by the Total button. Pulling down on that button revealed the result while rewarding a child for their efforts with the ring of a bell.
The Adding Machine could be reset using a rudimentary clearing mechanism. Holding down the Clear button while pulling down the sliders would reset the register to 0.