As mentioned, the "Sextet" part is only visible on the front, so even if all 6 of them get equal billing on the back credits, the artist ist still more than "Mal Waldron (any gropu name)" , Dolphy and Ervin are more prominent in the design. This is open to discussion, of course, and whatever people decide is fine for me.
What is displayed as the matrix# on the labels is indeed used as cat# on the cover.
BTW, I used to have this filed under Q for the group "The Quest" until thinking this was wrong somehow.... it is a bit like Reggae Dub albums, in a way
JJ, you are right, barcode, but I remember there was an answer to a querie by someone else a couple of days ago to do exactly that, so some more of mine will have it by now