Guys,
here is JE's 8 String Spyder shown at last years exhibition at the Metropolitain Museum


Greetz
Oliver

More photos

Great pics, wow! I'm curious about that one little round back plate on the lower horn. Looks like you could only access the pickup selector, but not the master volumes or selector switch?

Yeah looks like the master vols and the switch were front loaded. 

Greetz
Oliver (Spyderman)

Thanks for these pics Sypderman!

Wait a minute...

- PU selector
- Master Volume
- LED switch?
- Knob???

pickup selector
master volume #1
master volume selector
master volume #2

Mario,
you can see in the Won't get fooled again video (shot at Shepperton) or also in the isolated track video,
how John was using the two master vols. 
It was just to be able to switch by a flick of the switch between two master vol settings

Greetz
Oliver (Spyderman)

Saw this at the Met - their description:

Many thanks for sharing Ed!

Greetz
Oliver (Spyderman)

Now I got it, thanks Mica and Oliver.