Biconvex objective lens belonging to the terrestrial telescope inv. 3185. The aperture is 111 mm, the focal length 111.6 mm. It was given by its maker, Giuseppe Campani, to Ferdinand II de' Medici, as shown by the dedication engraved on the glass along the rim: "Ferdinando II. Serenissimo Magno Etrurie Duci. Joseph Campani faciebat Romae anno 1665." The glass has a slight red tint but is otherwise very clear except for some bubbles. The lens is well worked, but has some scratches.