Nearly 83 mm in diameter, this doublet was removed from unknown surplus military equipment. The lens is approximately 39 mm overall thickness, with a +8 diopter curve on the front surface and a -11 diopter curve on the rear surface. It doesn't seem to have a measurable focal length. There are minor edge chips or scratches in these items, but are otherwise in good condition. If you have an application for these, you'll be getting a great bargain!