Mamiya DSX 1000

From Camerapedia.org

Like the Mamiya MSX, the Mamiya DSX also came in DSX 500 or DSX 1000 models, and both use the SX series of Mamiya 42mm screw lenses, which have a lens mount lock (unlike previous Mamiya threaded lenses) and a mechanical pin which transmits the f-stop information to the camera, eliminating the need to stop-down for metering.

Links

• Ron Herron's "Collecting Mamiya 35mm Cameras"