Well, I'm not sure how I had missed it, but Amazon notified me that back in 2015 and then in 2016, John Mayall had released 2 live single CDs culled from live dates in 1967, with the Peter Green / Mick Fleetwood/ John McVie line-up. The recordings were made on a single channel reel-to-reel recorder at 5 different gigs; each of these 2 CDs has a mix of songs from those gigs. 

As you'd guess, the sound is bootleg quality. I'd call it "Good" quality, not "Very Good" nor "Excellent." It's a little fuzzy and boomy. The high ends can be harsh. It is not a recording I would play for my wife or for a casual listener. 

However, if you are a Peter Green fan, it is a real find. His guitar cuts through very nicely, and you can hear plenty of his subtleties. 

I am very used to John Mayall bootlegs as well as some of his archival recordings that have less-than-mint sound. With this line-up, it really helps that it's a small band with sparse arrangements. A bigger, busier band with more complex arrangements would sound murkier. Here it's just bass, drums, one guitar, plus Mayall's voice, harmonica, and keyboards. The playing tends to be economical and sparse overall; it ain't jazz fusion or prog. The warmth of Peter Green's guitar tone really helps. At times, the harmonica and organ can be a little harsh / trebly/ high end; likewise, when a solo section reaches a crescendo, the sound can be a little harsh. I am used to Mayall's voice sounding fuzzy on 1960s recordings, even in the studio!

But oh the playing. I've been listening to Volume One. "The Stumble," "San-Ho-Zay," "Stormy Monday," all mint. Peter Green really stretches out.