Dunno if I've ever seen a test pressing for a quad LP inside a completely finished sleeve before - normally this kind of thing is in a generic white sleeve with the information written on the outside of it in sharpie or ballpoint pen.
The date of the mix on the master tape (as seen inside the Quadio booklet) of 5-31-73 suggests the mix was done in anticipation of being part of WEA's first batch of QuadraDiscs in September 1973, but that it just didn't make the cut for whatever reason. Maybe they thought the mix was lackluster compared to the other ones they had available, or maybe they had second thoughts about releasing an album in quad that was nearly a year old by that point, especially with a new LP (Ladies Invited, which was released in November of 1973 - wonder if that one has a shelved quad mix too?) on the way in stereo.
