Ding, ding, ding. We have a winner. I don't have the full shot at work, but yes, it's a Meuller hydrant, 5-1/2" discharge opening. It's not on a sidewalk, but that's OK.
Oooooo..... so close. They say BZZZZZZZZZZZZZZT. No go.
Also, cut me some slack. It was hard enough to find something in my office that would be even remotely recognizable to most folks. It's mostly legos, 3D printer parts/prints, Strandbeest models and gyroscopic oddities.