This is the old two channel Dual Rectifier. It sounds really awesome, and pretty different from the three channel ones. I have heard people mention this before, so it was cool to experience.
I like how the control and screen grid resistors for the power tubes are wired in right between the tube socket and a terminal strip, not PCB mounted.
Mesa Boogie Dual Rectifier Solo Head preamp
Mesa Boogie Dual Rectifier Solo Head power amp