This compact cylindrical machine, with its single studded disc as transfer mechanism, was designed by the mechanic Christel Hamann from Berlin and patented in 1905. An earlier machine, the so-called Haack-Hamann construction (cf. Bölter ), had already been exhibited at the 1900 World Exhibition in Paris. Hamann’s machine, which first bore the name “Gauss” and was later, as an improved version, renamed “Mercedes”, can be considered to be the prototype of Curt Herzstarks ”Curta“, because when its studded disc is rotated by means of a crank, it engages cogwheels with radially arranged axles and thus transfers the entered number into the result mechanism. The Mercedes has one important improvement with respect to the Gauss, namely a second studded disc based on complementary arithmetic for subtraction and division. This may have inspired Herzstark’s complementary mechanism. Externally the Mercedes can be recognized by the additional addition/subtraction handle next to the crank. A detailed analysis by Ulf Hashagen  traces the interesting development of this machine, in which geoscientists also played a part. One has estimated that about 1000 of these machines were built, and the firm Reiss, for example, advertised them in its instrument catalogues in the years 1906 to 1914. Only a handful have survived. Their production came to an end when the Euklid 1 (FDM 6174) became available (cf. FDM 9465).