I've owned-
JP2C
Mark IVa (sold)
Mark III blue stripe (x2) (sold) (sold)
Mark III red stripe (sold)
Mark IIC++ DRG
Mark IIC, then +, then later ++ HRG (sold)
..and I just bought a late serial IIB Coli thanks to Racerxrated.
Other than the JP they were all serviced by Mike B. so they were the best they could be.
The factory DRG is effing amazing & there's a reason they sell for so much. If a guy couldn't afford the real deal I'd recommend a IIB loop mod or a III red stripe, depending on if they lean toward early or late 80s gain tones.