I can find no record of any gunmaker in the U.K. trading under the name Northcote during the 1800,s
In my opinion it is a ship,s gun. The ship in question being,The Steam Ship Northcote. The S.S. Northcote plied the Sask river in the 1870,s. The ship was a participant in The North West[Reil] rebelion in 1885. General Middleton Made use of the ship at the battle of Batoche May 9-12 1885. As such this gun could well be an important artifact related to this period of Canadian History. Recommend you contact the Province of Saskatchewan as they have archives related to the Reil rebelion that include pictures the S.S. Nortcote.
The gun pictured is Typical of Birmingham guns made by several companies, circa 1870-1900.
