Georg Hartman (1489-1564). As well as being a pastor of St. Sebald's church in Nuremberg, Hartman was also a mathematician and designer of instruments such as astrolabes, quadrents and various types of sundials. The dials with his signature were most likely produced by others, to his designs, and retailed by him. The maker's mark of a six-pointed star is normally associated with Hans Troschel the Younger (fl.1616-31), making it apperant that it was also used by an earlier maker, possibly of the Troschel family.