The only difference I can tell between the original Yashica Pentamatic ’35’ and the Pentamatic II (which came out in late 1960), is the standard lens that came with the camera body. The original Pentamatic came with the Auto-Yashinon, f/ 1.8, 5.5 cm fully automatic 6 element lens. Of course it has the unique Pentamatic bayonet mount and not the M42 screw mount. The Pentamatic II came with the Auto-Yashinon, f/ 1.7, 5.8 cm lens (pictured below). Both lenses were made for Yashica by Tomioka Optical of Tokyo. I imagine the 58 mm, f/ 1.7 lens was a bit faster than the f/ 1.8… but I don’t see why Yashica changed from the model I to model II and why they changed the lens… may never know either. The 5.8 cm lens is a beautiful lens and weighs a ton.