for my Stroud Audio Archive
I have recorded a chap who's grandfather served in the Boer War and WW1
His army record shows he ended up "attached" the MPSC in 1919 with his wages being sent to his wife which may be significant. By all accounts he never spoke of his experiences to the Grandson, even though they lived in the same house. He kept his "army tin box" (with his name on it) in the bedroom until his death. The Grandson still has his many medals.
I would guess the "MP" is Military Police (or Military Prison?) but other than maybe "Special Company" I couldn't guess the rest. Web Search doesn't reveal anything that is remotely helpful.

What do the Military Fans of this parish think MPSC stands for?