This instrument, apparently invented by Leonard Zubler, was made by Georg Zorn, about whom we have no information. It combines the characteristics of proportional compasses and the radio latino. The sides of the two main legs are engraved with several proportional scales. The central leg, which is fixed, ends in a ring that probably contained a gimbaled magnetic compass. The three legs are joined by two small jointed arms that slide on the central leg, indicating the angle formed by each of the main legs. The angle values up to 120° were shown on the central leg, which also displays the values of the sides of the polygons that can be drawn with different compass openings. Fitted with viewers (now missing), the instrument could be used for surveying. Brought to Florence from Germany by Prince Mattias de' Medici in the first half of the seventeenth century.