The William Norris mentioned by Gibster is still listed as a gunsmith in Ripley, Brown County, Ohio, in the 1880 census. He was born in Kentucky in 1807, and had a daughter still living in his household who was born in Ohio in 1840.
There were several gunsmiths named William Morris. Sellers lists one in Dexter, Michigan in 1867, another in Indiantown, Virginia, circa 1850. There was another one from New York, New York, who was issued a firearms patent in 1860, and a W J Morris, also of New York, New York, who was issued a patent on a gunlock in 1873.
There was also a William Morris listed in the 1880 census as a gunsmith in Sherman, Grayson County, Texas. He was 27 years old, born in England, and was a single man, living in a boarding house.
Horace E. Dimmick did indeed supply locks to the gunsmith's trade, but it is a bit unusual to see one on a rifle made very far east of the Mississippi Valley.