Addometer; Reliable Typewriter and Adding Co; 1900-1960s; 2010.432



About this object

Addometer; an early, mechanical calculator made to add, subtract and multiply. Manufactured in Chicago by the Reliable Typewriter and Adding Machine Co between 1900 and the 1960s.

The addometer consists of several dials with numbers, which are turned with a stylus to select the numbers for adding, subtracting or multiplying. The second dial from the proper left is numbered to 11, and the far proper left dial is labelled with quarters and eighths to deal with feet and inches.

The Addometer was very popular and together with competitors such as the Lightning Calculator were produced for many years until cheap electronic calculators were available.

This belonged to Sam McDowell who had a grocers/general store in the bush, and used the addometer there.


Reliable Typewriter and Adding Co

Maker Role


Date Made


Place Made

North and Central America, United States, Illinois, Cook county, Chicago

Medium and Materials

processed material, metal; processed material, leather; processed material, paper.

Inscription and Marks

Printed in gold on box lid: 'ADDOMETER'


h 30mm x l 305mm x w 77mm

Subject and Association Keywords

commerce, business, retail trade

Credit Line

From the collection of Owaka Museum Wahi Kahuika The Meeting Place "a rest on your journey"

Object Type


Object number


Copyright Licence  

All rights reserved