Objective lens with a diameter of 70 mm, a thickness at the center of 4 mm, and a focal length of 3,600 mm. It is chipped on the edge, probably because of a forced mounting in a ring. The glass has a slight red tint and contains many small elliptical bubbles. Still partially legible along the circumference is the inscription "Jacopo Mari... Fior...," which allows a definite attribution to Jacopo Mariani.