As Dans40x says, it's a Rem 40XC stock. They came in wood and Fiberglass. They were intended for NRA Highpower Rifle competition, but weren't particularly popular there. Today they're in use even less with the advent of Tube Guns and Space Guns for match rifle (non-service rifle use). The XC stocks were available from McMillan (who produced them for Remington), but I think you'd have to beg them break out the old molds. They weren't that popular when they were current on the highpower firing lines. Value? I think $400 to 800 is high. But Dans40X is right, it's now a "find the right buyer" kinda piece. Unscrew the buttplate or rail to see if it's wood or glass underneath. Being able to say it's a McMillan might get you more.
