This lens is an Achromat that is 40mm in diameter by 125mm focal length. The edge thickness is 9mm and the center thickness is 12mm. This lens is coated. The lens either has coating problems and/or cement breakage, that starts at the edge and goes towards the center about 6mm around the whole lens. May also have light scratches and edge chips. These will work great as an inexpensive finder objective or monocular objective.