I looked into the Count Dante stories out of interest in martial arts history in the past. Long story short, John Keehan was essentially a natural born streetfighter and later the youngest Black Belt in Robert Trias' karate system and was his midwestern. He ended up deciding that he would be more respeced as the master of his own system, which he claims was based on a whole bunch of secret systems that he had supposedly studied.
He took his streetfighting ability (which is not really questioned... his involvement in a large number of streetfights has been confirmed by everyone from the police to the Chicago Tribune to his opponents, friends, family and the courts), his karate knowledge, some boxing and wrestling he picked up, along with some kenpo that some other members of his organization were aware of and created the "Dante System." He launched alot of advertisements in comic books and sold a "dance of death" guide - although everything I have heard suggests he rarely or never used any of the foul tactics in the guide himself.
He did fight a large number of challenge matches in Chicago, as well as participating in dojo storming and ended up being arrested trying to tape dynamite to another dojo while drunk. He died in the seventies.
To their credit, his own sucessors (Bill Aguilar is now in charge of the system) don't try to pass off his claims as fact, but just acknowledge he lied about that part. They have kept up his flair for showmanship without the same claims.
Historically legit? Not really. Fighting legit? Keehan himself probably was, his sucessors and students not really.