Pardon my rudeness. Welcome to the forums from the Wiregrass! Your gun is a British service revolver that originally was designed to chamber the 38 S&W cartridge which is a larger cartridge than 38 Special. However, after the war, many of these guns were imported and modified to shoot 38 Special. If a 38 Special cartridge fully inserts into the cylinder, it was so modified. You can shoot 38 Special but expect the cartridge to swell and perhaps crack the brass. Also it has been refinished in nickel as others have noted.
Guy