This is a great anti-reflective coated cemented doublet achromat erector lens in the original military packaging from 1953. We believe this is used in one of the Simpson military instruments. Packed by Libbey Ownes Ford Co. 16mm diameter x 135mm focal length. 4.5mm edge thickness. We have a large quantity of this military collectible if you want to incorporate them into your project or design. Quality lens! Unused!