Those aren't actually Jerry's speakers; I think that's an extension of Brent's keyboard rig. It was a pair of 15s, a pair of 10s and a high frequency horn during that era. Garcia's cabinet is off to his left. Usually the 10s were JBL K or E 110s, those could be Gauss, it's hard to tell.
That arrangement went away when Jerry moved next to Brent in 82.
Here's a better look. You can see Jerry's 4X12 to the left, and Weir's cabinet to the right by the drum riser.
That photo is also interesting because it shows the monitors they had suspended over the stage pointing down as well as the floor wedges in that era.
In 79 they even had a Leslie over there, but I guess the wall of Leslies was loud enough to hear the organ across the stage. Notice the magic mystery knobs taped to the cabinet, no doubt an accessible level control for the keyboards and one for the Leslie.