The rod turned freely in its underground anchor, but the nut is apparently frozen to the rod. I deployed the bolt cutter on the cable and hauled the carcass into the Basement Shop:
Steeping the nuts with Kroil for a few hours relaxed them enough to submit to gentle suasion, whereupon the cable sproinged as the last nut released the clamping force:
As far as I can tell, the clamp hardware dates back to the pole’s original installation in 1940 and is in fine, if not pristine, shape.
The bolt shanks have an oval section matching the holes in the plate, so the bolts don’t turn and the crew needs only one wrench. They don’t make ’em like they used to!
I have no idea what I’ll do with these things, but they’re entirely too nice for the steel recycling bucket.