Thanks Paul, that is a Canon-made "Lens Mount Converter N" for FD cameras. I'm sure that you know that Canon never had an FD 35mm F1.4. They did made mount converters for Pentax screwmount and Exakta lenses, and perhaps others which I do not know about. Due to its relatively thin film register, the FD mount is great for mounting other manufacturers' optics to its cameras, though I've never found any adapters to put Contax-Yashica or K-mount lenses on an FD mount.