I've run across both versions, both spelled out...'Rawal Pindi' and 'Rawalpindi'; and on disks... 'RP' and 'R.P'

The roundels stamped on the butts of some pre-Lee rifles seem to provide a bit of a clue, as they're most often spelled out. IIRC, I've seen one on a Martini spelled with a distinct gap between Rawal and Pindi, and Brigadier-General H.A. Young, director of ordnance factories in India from 1917 to 1920, uses the spelling Rawal Pindi in his "The East India Company's Arsenals & Manufactories". Also some use the word 'Arsenal', some just the location, which would also seem to coincide with what turns up on some of the disks.

The thing is, that all of the disks formatted in this manner seem to coincide rather neatly with the names of Indian Arsenals...F.W - Fort William, AA or A.A Allahabad or Allahabad Arsenal (had an interesting conversation with Hambone from the K98kicon boards who holds the opinion that Alexandria might be another possibility there), F.A - Firozpur Arsenal. R.P or RP for the abovementioned Rawalpindi, and K.A, which as I recall, fits two possibilities, Karachi, and one other that escapes me at the moment.

There's certainly no rock solid proof that I'm aware of for this theory, but it certainly seems a possibility, and an interesting avenue for some further study/research.