Conto Model A

Coplanar Toothed Disc Adding Machine (ca. 1908)

The Swiss engineers Karl Karasek and Johannes Aumund, Zurich, developed this toothed disc adding machine, where the number circles on the top plate are rotatable by pointer handles. The first patent for this (adding machine) was applied for in 1906. The first series production was started in the engineering office of Johannes Aumund; production was soon transferred to Carl Landolt, Thalwil, who also carried out further development of the machine. Model A did not yet have a setting control mechanism; the setting had to be checked on the discs by means of the pointers. The set amount is simultaneously entered in the totalizing mechanism. The total can be read in the inspection holes outside the numerical scale. The pointers are returned to their original position by means of the lever at the top. This machine with the low machine no. 309 originates from early production by Carl Landolt around 1908. The model was produced until approx. 1911 and then replaced by model B.