The brass plate is cut to the contours formed by 3 arcs. The outer arc is a quadrant with a degree scale 0 to 90, divided to 5, subdivided to 1 with alternate hatching, numbered by 5. Two intersecting semicircular arcs have, in one case a scale ('? S ? RECTVS') of sines of angles to 90 degrees, 0 to 100,000, divided to 10,000, subdivided to 1,000 with alternate hatching, numbered by 10,000, and in the other a scale ('? S ? VERSVS') of versed sines 100,000 to 0, similarly divided and numbered. The plate is pierced, decorated, and marked in the upper section '? INSTRVMENTV<M> ? PRIMI ? MOBILIS ?'. The lower part has the arms of the Medici, the date '1568' and the signature of Danti in the form '? F ? E ? D ? P ? F ?'.
