If Earp did carry a 10" barreled revolver without a holster, maybe that's where Mae West came up with "Is that a gun in your pocket or are you just glad to see me?"Earpologist Jeff Morey, tech. advisor for Tombstone went through writer Stuart Lake's old documents and found a few copies of letters where Stuart asked various Earp friends if they might know the whereabouts of his extra long barreled Colt SAA. The barrel was quoted as 10" but Stuart changed it to 12" for his book Frontier Marshal. So, it appears Lake didn't invent the gun. Maybe Earp did, though. But if the gun existed it could very well have been the OK corral gun. A witness at the Earp's trial, the owner of the Bauer meat market a couple doors down from the gunfight site said Earp had a gun that looked "about 14-16 inches long". According to Morey a SAA with a 10" barrel is exactly 15" long. The S&W American Earp "might" have owned is in the Autry museum, but they won't say it was an Earp gun for sure.
What all this comes to is, we'll never know what he used. One thing. The Earps did not wear holsters. I think testimony had Virgil Earp putting his gun back in his wasteband after told the "cowboys" were disarmed right before the fight. Here's the Buntline article I got this stuff from...
Wyatt Earp's Buntline Special - Tombstone History Archives