This is a very rare 4-species machine built by Friedrich Weiss in Vienna, of which only three are extant: the two others are in the Vienna Technical Museum (Nos. 15530/1 and 15530/2). The Arithmeum one has the machine No. 106. The records of the Vienna Technical Museum note that their machines were “built around 1900 (since 1893)” and “built 1905 Friedrich Weiss Vienna”, which poses an enigma when trying to date the Arithmeum machine, which has no such inscription and whose construction is much more professional than that of the ones in Vienna. Thus one can only surmise that it was an almost completely hand-built prototype. Its construction principle still awaits detailed analysis, for which it must be opened up. Friedrich Weiss was a watchmaker in Vienna who also specialized in sales and service of 4-species machines. Thus the Burkhardt machine in the Arithmeum (FDM 7051) has the following inscription below the Burkhardt signet: “Friedrich Weiss Watchmaker Vienna”. It is very probable that Weiss not only sold Burkhardt machines but also endeavored to launch his own machine (this one) on the market. By deciding to use a switching pawl mechanism he was using exactly the mechanism that Curt Dietzschold (cf. FDM 7153) had tried to establish in Glashütte, Saxony, before Burkhardt’s time. The Weiss mechanism is, however, totally different from that of Dietzschold; viewed from outside it is much more reminiscent of the Heyde & Büttner of around 1883, a construction which also dates from a time after Dietzschold.