Forehand & Wadsworth British Bulldog Revolver

Picked up a Forehand & Wadsworth British Bulldog Revolver that appears to be in a 38 caliber. Some of the platting is worn off the cylinder but the action is pretty tight and the bore not too bad. Paid $35 for the thing. I check the bore and it certainly is 38 caliber. Anyone have any experience with this type of revolver. All number match. Serial is 264**. I checked on Gunbroker and there are a few for sale. Can't figure out what it shoots, but appears to be centerfire 38, but 38 what? Any value to it other than a nice paper weight. Thanks.

Black powder?

I partially dis-assembled today. Put all the parts into my ultrasonic cleaner. Water turned muddy after a bit. Pistol came out clean. Put it back together. While apart a nine mill round fits perfect in the cylinder. So my guess is 38 S&W. After the cleaning the action is much more smooth. Except for the old nickle coating which is worn off in places, it is not a bad small pistol. I am sure I will never shoot the thing.