The long lever also indicates it saw Equatorial service. Not always though. Considering when those rifles were built, they are very strong. Lots converted to relatively high pressure cartridges such as 303 British and others with even higher pressures.
The rifle appears to be complete which is nice. If the bore is in VG or better condition it should shoot well.
Del Selin's gunshop in Vernon, BC who is a paying site advertiser sells an insert which allows the use of a 45 Long Colt cartridge with reasonable results and much cheaper and easier than getting the reloading kit and rolling your own.