This is the excellent Penta Prism for the late Rollei TLR's such as the 3.5E 3.5F 2.8E 2.8F and possibly others. It allows you to shoot in specially low or high angles without the trouble that the waist level finder brings in those situations.
This one has moderate separation around the edges of the glass (see photos) but it is not visible while in use and will not affect your images. Cosmetically it is in good condition with moderate wear. There is a tiny dent on the top of the prism but it is minor and does not impact the function of the prism. It is not visible while in use. The mount shows light wear.
It does not come with a diopter piece.