Used before the invention of electronic calculators, mechanical adding machines were most often used for long calculations. This calculator was used in the Ballarat School of Mines Physics Department. Addition and subtraction were perfomed by turning the larger side mounted crank forward or backward. the smaller crank lever zeros the two registers. Two buttons are provided to set the machine either to clear the number entry with each revolution of the crank or to repeat the entry. The largest button resets the keybord to all 0s.
A calculator with shiftable carriage and digit separator rods between each row of keys.