This improved version of Hahn’s calculating machine of 1770/74 was built in Ansbach during the years 1805 to 1820 by the former Hahn-apprentice Johann Christoph Schuster (1759-1823). The inscription on the top-plate reads: “Rechnungs=Maschine von Joh: Christ: Schuster in Ansbach in Francken angefangen 1805 vollendet 1820“. The machine is more compact and has an improved setting mechanism: as with Müller’s calculating machine of 1783, the toothed rods are moved by turning knobs. Apart from that, it is identical with Hahn’s machines, which Schuster when young had helped to build. Upon the death of his master, he had in fact completed an unfinished machine in 1792. In 1804 Joh. Paul Bischoff of Ansbach mentioned the ‘Watchmaker Schuster of Ansbach‘ and reported that he had worked as journeyman with Hahn from 1778 to 1780 and had later married one of Hahn’s sisters. It is, however, also possible, that Schuster lived and worked with Hahn somewhat later during the 1780’s. In 1787 Schuster moved to his birthplace Westheim in Franconia and in 1790 to Uffenheim. He finally settled in Ansbach and remained there to his death in 1823. The calculating machine specialist Bischoff very likely met Schuster; perhaps this meeting even motivated Schuster to continue to develop Hahn’s machine, because Bischoff was also well acquainted with Müller’s machine. After completing his lengthy work on this machine, the original of which is in the Deutsches Museum, Munich, Schuster built yet another version during the years 1820 to 1822 which did not reappear until as late as 1993. Thus Schuster built three calculating machines in all.