Re: Humbuckers in Peter Green's Les Paul...
Sounds like A2 to me too. It was a '58 Les Paul.
A4 sounds very clear, ballsy and articulate. Lindy Fralin humbuckers all use A4.
To my ears, A2 accentuates the mids and A5 accentuates the bass and treble. A4 has more mids than A5 and more bass and treble than A2...kind of the best of both the A2 and A5 world.
A4 can be a little edgey and bright sounding if you're not comfortable with that much clarity and articulation.
Lew