Ed, I read the thread.
I have been collecting and studying Chevrolet 3/4" hex lug wrenches from 1960's and 1970's models since the 1990's for the purpose of finding the correct lug wrench for my 1970 Camaro SS350 long term project. I have still have about 40 or 50 still in my collection with various markings ("O", "E", "U") and some without any markings. Their dimensions varies along with the angle bend. I sold my NOS 3909176 lug wrenches after I determined that they were not correct for the 1970. Attached are photos of some of my lug wrenches with the "O" marking. I always thought that the letter "O" was for Otterburn but do not remember where I got that information. Apparently the letter "O" is for the Herbert E. Orr Company. I have been researching 63-67 Corvette and 67-73 Camaro parts for 4 decades and it seems that I still learn something new every day.
Dave