Probably worth finding out what states used ‘Chairman’ back in the mid ’70s.

I’d say Montana, Colorado or Nevada would be good candidates.

Of course, and if there even was a DMV letter, the guy could easily have thrown in Chairman to jerk chains.

"Chairman" could just be a generic term used.

Mike Rodelli’s excellent book points out several instances of his suspect exhibiting British influence.

Yeah, I’ve seen mention of it, like "salted beef", which is a British term for Corned Beef. There are several others. I’ve always considered them just indicators of being well read, as most of the supposed misspellings are actually just archaic versions of modern words. The guy seemed familiar with British literature. Pretty sure he wasn’t British though, as he had no accent.