Looks similar to the "Linspeed" oil finish we used to put on our stocks as kids. I think it's still available. If I remember it was a boiled linseed oil mixed with something else. Dried overnight, not like regular linseed oil. Gave a high gloss finish if you put enough coats on it, plus it was really waterproof. I use Minwax Wipe-On Poly now. Goes on like linseed, but is as durable a polyurathane and can be spot repaired.
Bill