The date of 1874 means that this is a Mk. I Martini-Henry rifle (sometimes also called an Martini-Enfield, after the inventor (Martini) and the place of manufacture (the Royal Small Arms Factory at Enfield)). This rifle was made in several variations, for issue to different troops (cavalry, artillery, infantry, etc.) and to know which specific version, we'd also need to know the barrel length (to get this, close the action, push a rod down the barrel, then measure the rod to the point where it stops). Unfortunately, this one has had a couple of pieces broken or gone missing; there was originally a sling loop at the front of the trigger-guard, and the tip of the "cocking indicator" (a large tear-drop-shaped pointer on the right side of the rifle) has been broken off. These rifles were originally chambered in 450-577 Martini-Henry (a cartridge that was a version of the older .577 necked down to .45 calibre), but were later converted to .303 before being replaced entirely by the Lee-Enfield series. HTH.
Just as a final point of interest, the "point-to-point" arrows stamped into the stock shows that this rifle was sold out of service (most likely to the soldier that originally used it in the forces, as this was an option given to them when they were passing out of the forces).
Gun control in Canada: making the streets safer for rapists, muggers, and other violent criminals since 1936.