Nice piece Gibster. Lucky you. I agree on the first initial being a "J", but I'm not seeing a "T". Looks more like the left side of an H or a K. There's something after that, but what? Have you tried shining a light down low and from the side so the light goes across the letters? Good luck on the ID, but it's a nice piece even without knowing the maker.
Oh, what about that muzzle? The square grooves seem to end just inside the muzzle. Is that an optical illusion or is the bore smooth?
-Ron