Yeah, just got a reply from Brian at J&J Cues: It is a modified 3/8-8 Uni-Loc Radial. He says that is all he knows about it. Perhaps a 3/8-8 Uni-Loc radial? How it was modified, this is not widely known I guess. May never
be known, exactly.
I had initially measured the TPI incorrectly at 10, because I included the 1st peak sitting at 0 as a thread. Five-peaks per 1/2 inch (including the fits tone at zero) = 8 complete threads per inch I think? So, it is 8 or very close to it.
Thanks to you and the other folks here I know a LOT more now that I did yesterday.

I am not even going to say why this info is important to me. But, you may be able to guess.
Well, no biggie. But, I do very much appreciate your interest and efforts in replying and checking. Thank you so much!