Summary

Alternative Name(s): Adding Machine

Exactus Mini-Add pocket model manual calculator with original box, instruction leaflet and vinyl wallet. Purchased by the donor's father, a returned RAAF serviceman and primary school teacher (FURTHER DETAILS AWAITED FROM DONOR), from Lendrum Pty Ltd, 328 Flinders Street, Melbourne. In October 1950 Lendrum advertised this 'pocket model', and a table model of the Exactus 'adding and subtracting machine', boasting that they were 'Ideal for Offices, Shops, Banks, Travellers, Ledger Clerks, Students, Storekeepers, Doctors, Dentists, etc'. The pocket model sold for 38/-; the table model was £8/14/6.

A 1949 advertisement in the Horsham Times expanded on its advantages: 'AT LAST! AN ADDING MACHINE THAT EVERYONE CAN AFFORD. Total appears instantly. No cogs, wheels or springs to go wrong. Pays for itself over and over again in mistakes avoided. All answers are "CORRECT" using "EXACTUS". If you wish to ADD or SUBTRACT Farthings, Pennies. Shillings or Pounds "Exactus" will speedily give you CORRECT ANSWERS Retail' selling price 37/6 Complete with WALLET'. (26 August 1949)

Derived from Troncet 1899 arithmograph or arithmometer, the Exactus Mini-Add consists of sliders behind eight vertical slots. The sliders can be moved by a metal stylus a desired number of spaces. Through sight holes above slots, the result of addition or subtraction can be read. Designed for pounds, shillings and pence.

Physical Description

Manual calculator with original box, instruction leaflet and vinyl wallet. The calculator is a flat rectangle with metal face, series of inner metal plates and a painted metal backing plate. The face features eight vertical slots, highlighted with black paint and unpainted silver to show pounds, shillings and pence. Visible within each slot is an inner metal plate, pierced to allow a metal stylus slotted to be inserted and move the inner plate. When this plate is moved, the circular hole (register) at the top of each slot shows a changed number. The stylus is slotted into tabs on the right side for storage. A hinged plate at the mid-front allows can be flapped to reveal either addition or subtraction context. A pull-out handle or 'slide' at the top of the calculator zeros the registers. The instruction leaflet comprises eight pages, made from two leaves printed on both sides and stapled in the middle. It includes 'Important Rules', 'Instructions', 'Practical Exercises', 'Checking' and 'Conclusion'. The box is printed in red and black on fawn cardboard, with a purple retailer's stamp on the back. The box is open-ended on both sides. The vinyl wallet is grey-coloured, with textured surface to imitate leather, stitched along edges. It is open on one end and part-way down one side.

More Information