Auto-exposure prism for Mamiya 645 / 645 1000S

Mamiya made 4 prisms compatible with the original Mamiya 645 and 645 1000S. This is the only one to offer automatic exposure. 

To use the prism, fit it on the camera and select the 'o' position on the camera shutter dial. The camera then operates in aperture-priority automatic mode. The prism controls the shutter speed, and displays the shutter speed via a needle at the top of the display.

In very good condition and full working order.