You mean like these? (See attached)
No, I've seen lots of original wrenches that didn't have the raised "O", and not all "O" wrenches were used on the Camaro. The company that manufactured the "O" lug wrench was one of several and they made lug wrenches for other models, and even other divisions as well. Not all of the manufacturers cast their Trade Mark on the wrench but I've also seen "E" wrenches.
Unfortunately, I have no idea what the "O" or the "E" stands for, but I would assume they're the trade marks for those particular manufacturers.
I believe Martin has a lot of wrenches in his "stash", so I've askd him to chime in. Troy also has a few original wrenches, so I've asked him to chime in as well.