Accura 12mm f/8 fish-eye

This lens was sold under various brands, at least Accura and Spiratone. It is a fixed-focus "fish-eye" lens with an unusual focal length that gives about 150 degree corner-to-corner view on an APS-C sensor and is somewhere between circular and full-frame on film (and not quite the 180 degrees marked on the lens). The aperture is settable to f/8, f/11, or f/16, all implemented using internal circular Waterhouse stops. As is common for fisheye lenses, the front element bulges out significantly; a distinctive shaped metal lenscap that screws onto threads around the front element protects it.