Many thanks on Marshall.
Your C~p~lton is Chatham, his barracks. The Ch, Ply, Po you see in Marines official numbers are Chatham, Plymouth, Portsmouth and it indicates which Marine establishment they entered upon joining service.
The R.F.R. indicates he had served his commitment pre war, joining on 18 February 1891, and joined the Royal Fleet Reserve. He was called up in the Mobilisation. To complicate things, further, there were A and B reserves, but that's a story for another time.
Keep up the good work.