Your hammer gun is from around 1889. If it does not have L.C. Smith Maker on the top of the barrel or rib it is a Transition Gun meaning it was made in Syracuse and assembled in Fulton when the company was sold or it is a very early Fulton gun with the Syracuse attributes. A picture would help more to identify it.
Also that would be the wrong butt plate as the Syracuse early Fulton's butt plate has a Setter with it's right foot on a rock.