Its currently unknown.
The "FR" stamp in wood appears on both rifles (many evidently in excellent condition), and also new/unused butt stocks, forends and handguards. Ergo it appears to be nothing to do with the similar British military "condemned" mark stamped into the metal butt sockets of scrapped rifles.
The font used does strongly resemble that associated with POF rifles - those assembled in Pakistan out of what appear to be a mix of British and locally-made parts. Some POF rifles have the actual same "FR" mark.
My own thesis is that "FR" is a property mark applied by a commercial contractor who was gathering together a large quantity of rifles and parts for export to a customer - quite possible Pakistan. Possibly this contract was blocked (as were most arms sales during the first India vs Pakistan wars) and so this material appeared on the surplus market.