Dan Healy is selling it, the guy who modded most of Jerry's rig. It does not have the 90's rack mod because it was not the one used in his live rig, at least post aug 79.
Closing of Winterland new yeara eve 78 shows the gray knob in use as well.
Disclaimer: I make and sell Buffers. I also sometimes Modify, Build and sell preamps and amplifiers. My opinions are not intended to be sales pitches. I am a one man shop and prefer to spend time with my wife and family, i work full time on call and love to spend my spare time doing other things. I only make, modify or build things for those that seek them.