Pictures would definitely help, but it is not impossible to make a couple of generalizations. Many of the Commonwealth guns were modified to take .38 Special ammunition in addition to the .38 S&W round (which the British called the .38/200). If you have a converted gun, its value declines because it is no longer in original condition. Such a gun might be worth $150-225 for starters, maybe a bit more after a close analysis.
If the gun is an unmolested British Service Revolver, basic value is probably $275-325 for a gun that is mechanically sound and not too beat up on the surface. I am a little worried that you say yours has no finish, because that may mean the wartime phosphate finish (like Parkerizing, but called Black Magic by S&W) has been deliberately removed. If what you describe is actually just a very worn Black Magic finish, that is actually good news from the point of view of collectors. But it remains the case that so many tens of thousands of this model were made that there is no scarcity premium. Even in 98-99% condition, a Commonwealth Victory would probably not sell for more than $500 unless it had some special distinction.
So that's the fairly wide range you are looking at. Pictures would definitely help us narrow the possibilities.