Its actually called R3M, just for technicality.
I have a R3A myself, and I got a 1958 Jupiter 8 with the CV adapter. Reason why I got one actually was that Im new to rangefinders and I didnt have enough money to shell out for something decent.
I did a CLA in my room in about 3 hours (half of that was figuring out how the lens worked) and the lens is actually very sharp!
Love the camera, love the lens.