I would vote to classify them as
Classic Vintage Rolex - (For the Purist - no discussion or interpretation)
Four digit Model Reference up to 1987
Vintage Rolex - Generic term to encompass Classic and Transitional in the widest sense
Transitional Models to include 16660, 16750, 16800 etc
These models are the ones that combine certain element like matt dial with sapphire crystal. Glossy wg circled index markers with Plexi-glass plastic crystal etc.
Neo Vintage Rolex
These models take us up to 1998/99 as Marcello pointed out.
The neo vintage segment I will not really attempt to define but why not it could include discontinued models or new Classic "Rolex Milgauss GREEN CRYSTAL ~ 116400GV". This could become the moving segment. Ok, Neo vintage does not sound so cool but...
Bill