The Adder

The British engineer Arthur James Postans (1867-1940) from South Kensington, London, applied for patent for an adding machine in 1902 in several countries. The British patent №GB190224868 (see the lower patent drawing) and the German patent were granted in 1904. The next year Postans obtained a US patent also (№786839). Later Postans received patents for the same device, or improved devices, in Canada, Switzerland, Sweden and 3 more British patens.

Adder patent drawing

The Adder patent drawing

The machine (see the lower photo) was manufactured in London since 1908 till 1920s and sold under the name Adder. The dimensions of Adder are 120 x 180 x 115 mm, weight 1.71 kg. It was a single-column single-axis adding machine with three results dials and a ten-key setting mechanism. The three dials are mounted side by side behind the window at the top of the machine. The setting keys are numbered from 1 to 10 and operate on the right-hand (units) dial only. An automatic tens-carry mechanism advances the tens and hundreds dials as required. The clearing lever at the left-hand side returns the three dials to zero.


The Adder (Courtesy of Mr. John Wolf)