Gunner's caliper consisting of two straight legs curved near the ends. The curved parts carry a degree scale on one side and a gimbaled compass on the other. The compass is fitted with an equinoctial dial. The legs have perforations for the sights, now missing. The plumb bob is also missing. One of the legs carries a hinged graduated arc that slides on the other leg, measuring the angle of aperture. On the hinge is depicted the lion of Saint Mark. One leg is engraved with the name of the inventor, Lorenzo Batecin. Provenance: Medici collections.