The "Addiator" side for addition and subtraction, with the operating stylus in its holder.
The slide-rule side.
Kingson Four-Rule Calculator
Is a Slide-Rule on one side and a 6-decade "Addiator" type calculator on the other side.
For use with totals up to 999,999, or, by putting the decimal point two places from the right, currenccies up to 9,999.99
Addition and subtraction using the "Addiator" type calculator (see the Addiator in this section) and multiplication, division, square roots, and reciprocals using the slide rule.
160 x 40 x 8 mm (6.25" x 1.6" x 0.3").
1960s to early 1970s.
Made in Hong Kong.
This was a way of incorporating the full four functions, as well as square roots and reciprocals, into a pocket-sized calculator which was much, much cheaper than the early electronic calculators.
© Text & photographs copyright Nigel Tout 2000-2015 except where noted otherwise.