This is how I understand the different revisions of the Revolution amps (I think it is fairly accurate):
The first production run (apart from any prototypes) Revolution is labelled "Revolution1" as can be seen in the picture of mine. It had a Choke (circled) as part of the circuit.:
The surface rust was on those screws when I bought it new .
The Choke was replaced with a resistor and that was "Rev1" as in your picture.
Then the Output Transformers were upsized, different tubes, etc... and became the "+" Series.
Okay cool thanks for the help guys.. does anyone have one for sale in the nashville area or in Marquett MI? I am going to be there for a couple of weeks...starting tomorrow.