Howdy
It's a six shooter, not a five shooter, right?
If so, you have a relatively rare revolver.
Known as the 38 Winchester Double Action, it was built on the same frame as the more common 44 Double Action.
It is very easy to confuse these guns with the smaller 38 Double Action, chambered for 38 S&W, if one does not have any thing in the photo to compare to for scale. Here is a photo of a 44 Double Action and a 38 Double Action. The 44 is the larger gun. If yours is a six shooter, and not a five shooter, you have a 38 Winchester Double Action.
The fact that your revolver says 38 Winchester CTG means it is the larger gun. CTG simply means Cartridge. 38 Winchester was the way Smith and Wesson referred to the 38-40 cartridge, also known as 38 Winchester Center Fire.
This is a rare gun, there were only 276 of them made, between 1900 and 1910. It is the rarest of all the variations of the 44 Double Action.
Yours is not in pristine condition, it shows evidence of being refinished, which diminishes its value. But it is still a rare gun. No, I am not going to guess what it is worth. In 2006, one in "fine, 40% condition sold at auction for $2875.
P.S. The serial number should appear in four places on this gun. Underside of the butt, rear of the cylinder, underside of the latch, and next to one of the ears of the barrel extension. These last two places can be difficult to see.
Here is the SN on the underside of the latch on a New Model Number Three.
And here is the SN on one of the ears of the barrel extension.
You should see the same SN in all four places, insuring the gun left the factory with those parts.