CTG means cartridge.

Info provided is very scant but the serial should not start with a zero. Very possible there's a letter S prefix.

My guess based on the extremely limited info provided is that it's a 1905 4th Model Hand Ejector Military & Police Model made between 1947-1948 (assuming the presence of the S prefix).

Could be blue or nickel with 4, 5 & 6" barrels most common.

Does it look something like this?