After years of researching the records of chip sales to the old illegal clubs, here is my opinion.
Mr Vaughn was the man that actually ran the gambling for the owners of the REX Club. He would have been the man to take any heat that came down. He may have run other illegals in neighboring states also.
OR
He might not have been a real person. Sometimes club owners went to a lot of trouble to cover their operations including making up names and having the chips mailed to mail drops, sometimes in neighboring cities or even states.
Good luck on your quest.