Thanks, Circuit Man.
I figured that out after posting this.
I was wrong about the Sangamo manual; the method of connecting a 240V meter for 120V is on page 50. You open the test switch and hook the neutral to it with a fork terminal, then the hot goes across both current coils in series. So you would see a jumper between terminals 3 & 4, and the neutral pigtail is actually terminated separately. That appears to be what we're seeing in this pic.
