Looks like one of the imports from Malaysia. The 1st KOYLI were one of the units involved in the Malay Emergency and perhaps they ended up supplying some of the arms to the Malaysians. I’ve never seen any LE unit marked like that before and I don’t know what the R means. The only mention of an R in Skennerton’s book is for an R on the barrel knox form indicating rust in the chamber.
If the barrel and bolt match the receiver that’s good, if the foreend and magazine match even better. If it has a good bore and functions in all other ways then that’s a good price these days. It’d be either a Fazakerley, ROF(F); or a BSA-Shirley, M47C.