When the Leica camera was born in the early 1900s, it was the first practical 35mm camera to use standard 35mm cinema film. In 1930, Leica introduced the Leica I Schraubgewinde, which used an interchangeable lens system based on the Leica LTM (Leica Thread Mount) 39mm screw thread.
Want a peek of the inner workings of Leica’s early LTM camera? Today’s your lucky day. In its September 1939 issue, the publication The Cine-Technician published an interesting cutaway diagram of the Leica camera. Along with a Hektor lens, the illustration shows the guts of the camera and the main components that make up the revolutionary photo-making device.