I'd say your guess is on the money .
Sounds like a 1911 Mklll RSAF Enfield , that has been factory repaired at Ishapore Rifle Factory ,India .
RFI is for either Royal Forces (or Factory ?) India .
The P , on the barrel knox . is for replacement barrel.
ISA is India's post independence stamp.
Is there any evidence of 2 crossed lines over the P thats on the buttsocket ?
I don't recall what the bolthead stamps are...
One thing fersure , this rifle speaks with a helluva lot of history !
X 2 for picts...