Those tabs or ears on the pivot seem to vary by model, size, and year of manufacture. Logically, I would assert that the diameter of the pivot pin should determine how many ears can be spaced around it.
Certainly some manufacturers could have had preferences for four- or six-ear pivots, but I don’t think it’s a reliable identifier.
Usually with Bonney pliers (which I think they always outsourced), I assume they were made by Utica, unless (like checker-dot grips) there’s contrary evidence. Not just after 1964, but throughout their histories, Bonney and Utica pliers share design features (e.g. depressed diamonds grip). But Crescent and Utica bear a lot of resemblance (not least in model numbers), and there’s the marked Champion DeArment example, as mentioned.
I would offer more Utica images, but the location, mounting position, and lighting on my display make the ears VERY hard to photograph. I took pics of ten pliers, and most didn’t clearly show the feature. MOST of my examples have four-eared pivots, but here’s a six-ear.