I am trying to sort out the differences between the various Mamiya RB67
lenses. I have the categories down as:

pre-C
NB
C
KL

KL is the current line of lenses and they are generally highly
recommended in what I've seen. Do the classes differ mainly in how they
are coated, or are there other significant differences that make a
difference? "NB" lenses appear rather affordable and would fit my
budget, but what are their drawbacks compared to the later models?

Some knowledgeable input on these lenses would be greatly appreciated.

Thanks,

Stefan Engström