Identifying Power Transformer - I think Marshall

[marshallnoise]

About 15 years ago I was given this Power Transformer that is unidentified by me. I remember being told by Jeff Snider that it belonged to a Marshall dual monobloc rack mount power amp. I googled pictures of those and it wasn't out of the gold/newish ones. If anything, it was out of my old Marshall Series 9000 50/50 rack mount power amp.

Here are the pics:


And here are the readings I got from testing every lead against itself:


What I want to know is:
1) What is the blue wire? Most Marshall stuff shows it as common.
2) What are the orange wires for?
3) I know that the greens are 6.3vac heaters
4) Reds are HT
5) I think yellow is rectifier 5v (no way to tell until I test voltages from it)

If I were to apply voltage to it, I assume black goes to one side of a power cord and the black/white goes to the otherside. Where does ground go to?

Thanks for your help.

Paul

[marshallnoise]

I applied 120 VAC to the black/white and black leads and got the following readings:

Yellow to Yellow - 23.5vac
Red/Yellow to Red - 355 vac
Red/Yellow to Red/Black - 356 vac
Orange to Orange - 122 vac
Green to Green/White - 3.37 vac
Green/Black to Green/White - 3.37 vac

Pretty clear to me that this is a Marshall style transformer. Thing weighs about twice as much as a JTM45 OT.

Safe to say this is a 350-0-350? Would it be suitable in a JMP50?

[marshallnoise]

And what the hell is the blue "common" line used for?