It appears to be a "Buntlne Special".
Beyond that the pictures don't give me enough information to be certain.
According to folklore, author Ned Buntline ordered the gun(s) from Colt, standard SAA but with a 12 inch barrel. Gave one to Wyatt Earp,,,,,
there is a Wikipedia page on this, which indicates most of the folklore is false or there has been no evidence found verifying it...
Colt did make some "Buntline Specials" when they resumed production of the SAA after WWII, and other companies have made their own clones to cash in on the cowboy craze from the 50s on up.
Generally speaking any single action revolver with a barrel 12" (or just longer than 7.5") is sometimes called a Buntline Special, no matter who made it, or when, or caliber. There are/were Buntline .22s and other calibers as well.