Upload & Sell: Off
I'm almost certain that XR means X-Ray, so that would be a X-Ray lens. I also have a Rodenstock XR Heligon 75mm f/1.1, but this one has a FL-mount (converter is on the way).
Camera is a 450D. And forget about easy picture-shooting. I have to focus by moving my tripod at focus distance of about 5cm (from front of the lens to the object). But I see it as a challenge.