I have somewhat of an anomaly of an amp, its a MKIIb with a serial number in the early 10,000 range. The knobs are not the concave silver, but the solid black like the IIC's, it has a IIB front panel, but it passes the loop test. Tonally it has mondo gain that is very smooth, not harsh like some of the III's that I've played. I don't even need to get the gain past 5 and I'm getting 80's Metallica easily. The clean is also very smooth and glassy, and there's no popping in the footswitch. Can any boogie experts out there explain this amp?