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.
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum