Demos II Calculator

"Was constructed in Switzerland (overall length 14 inches) by the firm of Theo Müggli in Zurich. It's working principle makes it stand apart from practically all other contemporary machines: back and forth rocking toothed segments that made intermittent contact with the counters.  Mechanically it only permitted to perform additions, so subtractions had to be made by means of complementary digits. Being cheaper than other machines was it's main (and perhaps only) selling argument." Freddy Haegens.

Courtesy of: Freddy Haeghens

X-Number World of Calculators