Well, I didn't read your initial post comprehensively, or I'd probably have realized what you were saying more subtly than I caught.
The pivot style resembles what I've got on my Greenlee, but isn't quite identical. There only but so many ways you can make a pivot like that. Maybe one of the companies recognized that the other company's design was just right and, rather than making some subtle change, got permission for (or, if not patented, just borrowed/stole) the design from the originating company.
I have no idea how fierce the competition was. If they were neighboring companies, they may have cooperated on stuff to fend off other companies.