The Fenian Brotherhood were a privately funded paramilitary group of Irish immigrants living in America whose goal was to put pressure on the British to leave Ireland. To do this, they conducted multiple raids into British-owned Canada to attempt to force such concesions.
The raids failed to get any traction, but this rifle was one of the more interesting things to come out of the event. This is a Needham brothers Conversion of a surplus Civil War musket chambered in .577 Snider.
