Voigtlander Bessa

Does anyone know the difference between R2 and a type R Voigtlander Bessa 35mm camera?

I understand that it is on Google and can not find a definitive answer. A good answer is that research could mean reflection as in SLR and R2 is the second version. However, the R stands rangefinder and was constructed as an alternative to mounting screws and rangefinders of the Leica M series (M series Leica are still made today) The "R" is a montage of thread of the body that can use the mounting screw old Leica lens and the lens Voightlander The "R2" is designed to use the Leica M mount series lenses Leica lenses

Voigtlander Bessa R3A Shutter Issue