Cardboard ring that contained an objective lens (now missing). The maximum diameter of the ring is 70 mm, the aperture 50 mm. The inscription ("Vang. Torr. 1644 3 1/2") indicates the maker (Evangelista Torricelli) and the year of construction, and suggests that the ring was to be used with an objective with a focal length of 3.5 braccia (1,900 mm).