There is a Model with a 4.8cm/F2 lens as I have one. When I first purchased this camera approx. 10 years ago I assumed it was the lens the model was designed with, but found out later the much more common model had the 4.5cm/F2.8 lens. I will assume the F/2 was first in design and for whatever reason Mamiya switched to the F/2.8 lens potentially for economic reasons, but I do not know the true reasons. I also have the original Mamiya lens hood for the 4.5cm/F2.8 lens Model which I have with two other backs.
Have never tested either camera with film as when I purchased these, I always had intention of testing but bought way too many cameras in a short time, and never made it back to them. Always knew the F/2 Model was much rarer, but never have seen any information about these cameras, other than a write up in a Pop Photo, circa 1958 when the Mamiya Magazine 35 was released.
Gary Hill