Still looking into this, trying to puzzle it out.
All evidence suggests that the above photo was Watkins Glen Summer Jam 1973. Have found some other interesting evidence and it will take a few days to assemble everything into a coherent timeline understanding.
The above photo, at this point in my understanding, was most likely from Friday, July 27, 1973. On Friday the stage was in constant flux with the Band and the Dead. Stuff was getting placed and moved around constantly. Since this would be the soundcheck, probably the first set, when it was still slightly daylight outside, you can see that things are scattered around to some extent. For example, one of Bill's drum-kit cases is on top of a speaker, and it may be that the guy to his right is a roadie, tightening things on one of his cymbal stands. The headless phantom!
From DeadBase XI, Weir just cut off his ponytail a little over a month before, and is sporting a new look. (Fred Heutte 6-30-73 review)
Let me sort this out, and I'll get back with pics. Should be interesting.