OK, finally able to circle back on this. I can confirm the four "known" '77 recordings made with mics at the sound desk are:
Richfield, OH Feb 17
Milwaukee Feb 22
St. Louis Feb 28
Townson, MD March 13
these four tapes all came to JEMS from the same source and are marked "stage mics."
A further search of the JEMS vault revealed one additional recording also marked stage mics from another source, and that's New Haven, March 18. It is missing the first two songs and is presumably the second source noted on Brucebase as excellent quality and "most likely recorded by Bruce's sound crew."
Transfers are forthcoming and we'll dig into this project soon along with a few other '77 tapes.