this is a pin hole adapter for a polaroid pack film camera. You just remove the existing lens and cement (we dont like to say glue) this to the opening. It has a .0177 hold drilled into a piece of alum which is cemented to a steel washer. They are both sandiched between layers of masonite front and back. the blue knob is a magnet that is both the lens cover and the pin hole shutter. Take it off count then put it back.. for sale on ebay at this time lol.