Hello, Shane Tuttle. I believe that rifle is a Snider conversion variant of the P1853 .577 Enfield muzzle loading rifle.
The later Snider conversions were made up of new made parts, as original muzzleloading one were depleted. Conversion began in 1866.
In 1871, thr Snider was replaced as the main infantry weapon by the .577/.450 Martini-Henry rifle.
The British then regulated the Sniders to native troops.
From the looks of the bolster/nipple alignment with the hammer, and bolster to plate fit, someone re-converted it back to muzzleloader..perhaps when they could no longer obtain the Snider ammunition?