This sale is for a little used Mamiya RB/RZ67 Cable Release Reverser, generally intended for use with the Mamiya RB67 and RZ67 75mm f4.5 Shift lenses, plus the Mamiya 645 50mm f4 shift lens, where the lens mechanism blocks access to the cable release socket.
This handy little gadget has absolutely minimal signs of use. It screws into the normal shutter release socket on your camera, with the shutter release cable now pointing backwards instead of forwards. A very rare item. This one comes complete with a short cable release.