Hi, I've just come across an M mount Canon 135mm RF lens. I've had Canon LTM lenses before, but this thing has a Leica M mount and absolutely does not have an adapter on it. Ever seen any others like this?
This is a new one on me. My guess is that it's a custom one-off job. You may want to post your note to the folks on RFF (Rangefinder Forum). Lot's of knowledgeable Canon-folk people there, most notably Peter Kitchingman who is writing a book on Canon rangefinder lenses.