The quadrant has an unusual alidade formed by two small bars hinged at an angle like a pair of dividers and joined at the ends by a 30° arc. Both the alidades and the straight edges of the quadrant are fitted with viewers. The rim carries the degree scale and the shadow square, while the entire plate is occupied by the sine quadrant, or reduction quadrant. The inscription states that the quadrant was made by Giacomo Lusverg in Rome in 1686. Provenance: Medici collections.