Proportional compasses with two flat legs, engraved with several proportional scales that give the limb its characteristic profile. The backs of the legs carry an arithmetical scale, a geometric scale, a scale of cubic roots, a polygon scale, and a metal scale. The front displays a chord scale, a tangent scale, the "added" scale (also found on the Galilean compass, inv. 2430), a polyhedral scale, and a scale of the ratios between volumes. Signed by Antonio Costa, about whom we have no information.