This lens has almost the same angle of view as the Mamiya 100 mm 1:2.8 SX lens. Why Mamiya offered two lenses so close in focal length with the same maximum aperture is still a mystery to me.
There are a few design differences between these two lenses. this one has a nice built-in lens hood (with black flocking material inside). Its smallest aperture is f/16 instead of f/22 with the 100 mm lens. This lens has only four lens elements (the 100 mm lens has five elements).
I´m curious if there was a significant price difference between these two lenses back in the 70´s. I think the 100 mm lens is harder to find and might be a newer design. I haven´t tested the optical performance of the two lenses.