Buddy of mine just bought a S&W Model 57 from an estate sale. From all the documentation I have found, this Revolver was only available in .41 Mag. Issue is this revolver is in .44 mag. Was it a rebarrel cal change after factory purchase or did it come from factory like this? It looks original with no more than a box of ammo through it. It's a N frame. Could this be an error from the factory or did they just use a N frame that was marked Model 57 for a Model 29??? Any thoughts??