This is an unmarked Petzval-design brass lens for large format cameras. Likely from a projector- there is no diaphragm or slot for Waterhouse stops- it features rack-and-pinion focusing and pretty decently clean glass, free of fungus, with minor marks from cleaning over the last, like 100 years or more. Focal length and aperture are unknown. Includes a threaded flange for mounting to a lens board (not included). Will cover 4x5.