It appears to be a MkIII, dated 1879 which would make it an early one. Good bore, nice amount of bluing left, but has areas of widely scatteredlight pitting. Nice butt roundel, and a surprise on removing the buttplate. Please see pics.
Here is where it gets interesting. Definately a name, Kerley, date of 1907, and a placename of Ft. Williams.
Now, would this rifle still be on issue at such a late date? What do ya'll think?