Mechanical calculator, direct key and printing, Addo, metal / Bakelite / paper, made by Aktiebolaget Addo, Malmo, Sweden, 1923
This object is part of a collection relating to the history and development of calculating devices assembled by Assoc Professor Allan Bromley of Sydney University, comprising mathematical instruments, slide-rules, mechanical and electronic calculators, electronic analogue computers, computer components, kit computers, education computers, and associated ephemera.
Allan Bromley was a lecturer and researcher at the University of Sydney Basser Department of Computer Science from 1978 until his untimely death in August 2002. He specialised in Computer Architecture, Computer Logic and in particular the History of Computing. He was regarded as the world authority on Charles Babbage's Calculating Engines (instigating the building of the Difference Engine No.2 at the Science Museum London) and the Antikythera Mechanism and had extensive knowledge of calculators, analogue computers, logic, stereopsis, totalisators, clocks and time keeping and mechanical engineering.
This calculator with rack setting was made by Aktiebolaget Addo, Malmo, Sweden, which has been making these since the 1920s.
Both printing and non-printing models were made, and there was also a special model for non-decimal English currency.
This particularly model is decimal and has a printer. It was introduced in 1923 to sell for Swedish Kroner 360 (ca. A$72).
The amount set up in this machine may be checked for accuracy in the check mechanism, and corrections may be carried out by resetting buttons, before the result is transferred into the result window, using a black Bakelite crank. Inscribed complementary digits are used for subtractions. This model has a printer with a roll of paper located behind the machine, and the paper runs underneath a tear-off bar and advances automatically. Inking is by means of a coloured ribbon.