Medis rangefinder accessory in box, imperial, shoe mount, made in Germany

This is a vintage focusing accessory for rangefinder and zone focus photography, made in Germany by Medis. It would look wonderful on your Leica, Canon, Nikon, Voigtlander, obscure Soviet, or other vintage camera, and it would be very useful. This particular item is marked in imperial units (feet), and is in good condition. There's one blemish, visible in the photos, and of course the shoe has some wear marks. The box is included. I don't have the eyeballs or the equipment to thoroughly measure the calibration, but I've used it and it definitely functions. The wheel turns smoothly and I can easily find focus.