Discuss .. I hear flats..
Based on these"Van Halen 1"... Got a media on this to make it a little easier for the rest of us to take part in the discussion?
I wouldn't rule out groundwounds (which existed back then, by D'Addario and GHS and possibly others) :
beside the amp saturation, there is some growl I don't usually associate with true flats (with exceptions), but finger noise from rounds is either filtered out or not there to begin with. I may be wrong.