Shiftless, RTM, four.cycle and Username - thanks for all your research help!
d42jeep, good find on the Harrold for another teardrop hole adjustable. However, the side lines on that, near the adjuster screw, look different than the Wright and the Great American. Also, the few Harrold pliers I have come across were not well made. This Great American wrench IS well made. (And, great collection of Barcalos you have there).
Lugz - I'm impressed with your capacity to dig up related facts of past posts - awesome brain. That WRIGHT adjustable and the GREAT AMERICAN have to have been made in the same place - the question is WHERE? With the dearth of information on Great American in the 20th century I'm inclined to think it was NOT the manufacturer or there would be more info on the company?
So - still stuck with who made these? Wright? Great American? Barcalo? I don't know enough about manufacturing techniques to speculate - could Barcalo have combined their teardrop hole and the their single panel into one wrench to make such a version for others, or would that have been impractical?
(If it would be helpful, I could take measurements of thicknesses or other components to compare with one of d42jeep's 6-inch wrenches?)