Actually, the pistol in the picture is a replica of an 1851 Colt .36 cap and ball revolver converted to .38 cal. I have one just like it. Very common in the Old West. I have read that the shot fired was a .45, so if it was a converted cap and ball revolver, it would likely be a .44 1860 Colt Army converted to take a .45 long Colt cartridge.
The earlier photo presented was that of a dragoon replica. We now know that was incorrect. In movies, even when they use “cap and ball” revolvers they’ve been converted to use cartridges to make the armorer’s job easier. We are also likely running into the fact that modern journalists can’t tell the difference between an open-top colt and an open-top BMW.
CC