rxmd
May contain traces of nut
The M5 has four framelines, the same four as the M4 in fact. I guess it was called M5 simply because it was the M4's successor model.M5: five framelines, built-in meter
Well, the M1 was simplified in that it doesn't have a rangefinder. It does have a viewfinder; the MD doesn't have even that. 🙂M1: M3 for the visoflex and microscope and copying jobs
MD: an M4 for the same purpose as the M1 (correct me in these last two if necessary, please).
I'm not sure about the M4-P's "P" standing for "professional"; it also has six framelines, just like the M6. I think in the end we can only note that the naming scheme is really, really confusing and that it's not worth trying to find logic in there 🙂
Philipp