it doesnt exist,..
the major part of the greenback sound is it's 25 watts is over driven and distorting,..
They are speaker manufacturers, they are British sounding.What is scumback? I don't know what this is.
The 50w WGS Invader is quite good. I'm not saying it's *exactly* a greenback but has a very similar flavor, you can certainly push it hard with a 50W amp, perhaps too hard