That 300H&H is awesome. Looks like it was made around 1950 +/- 1 year. Serial # probably around 150xxx. Obviously it is missing a front sight and hood, but a damn nice collectable rifle. Definitely has some wear. I'm betting it was one of your grandfather's favorites.. You can tell, he carried it and shot it more than the others. I don't blame him. I'm not going to give you an estimated value on that one because you should probably keep it and not be temped by the almighty dollar.