And more ... with a nice photo of it: https://blog.scienceandmediamuseum.org.uk/detective-camera-stirns-waistcoat-camera/ https://blog.scienceandmediamuseum.or

And more ... with a nice photo of it: https://blog.scienceandmediamuseum.org.uk/detective-camera-stirns-waistcoat-camera/ https://blog.scienceandmediamuseum.org.uk/detective-camera-s... Disc shaped and all metal in construction, at first glance the camera resembles a cross between a frisbee and a hip flask. Thin enough to be worn unobtrusively beneath an ordinary waistcoat, it hung from the photographer’s neck on a strap. The f10, fixed-aperture lens poked through a buttonhole of the waistcoat and, as a further aid to concealment, was designed to look like a button. Exposures were made on a circular glass plate that was rotated after each exposure by turning a knob protruding from the front of the camera. Six photographs, 40mm in diameter, could be taken on each plate. Rotating the knob also set the rotary shutter, which was released by pulling on a length of string which dangled from the bottom the camera.