Biconcave eyepiece lens mounted in a wooden ring covered with cardboard. The diameter of the lens is 27 mm, the focal length -84 mm (the negative focal length means that the lens is diverging). The glass, which has a slight green tint, contains elliptical bubbles. On one side of the ring all that remains legible is the written word "braccia," a unit of measure indicating the Florentine origin of the lens. The whole inscription is, however, preserved in an old catalogue: "Di braccia 5 1/2." This eyepiece was therefore to be used with a telescope of 5.5 braccia (3,210 mm). The lens can be dated to between 1640 and 1660. It may have been made by Evangelista Torricelli, Ippolito Francini or Jacopo Mariani.