In "The Hobbit", the party finds a troll's cave with a stash in it. They find a few swords of elvish make, and on the way out Gandolf finds a short sword to give to Bilbo. When he hands it to Bilbo, he tells him, "it's made from elvish steel which means it will glow when orcs and goblins are near by". His statement was broad, not specific to the sword that he was giving Bilbo, yet the other swords (the one Gandolf had as well as the goblin cleaver) did not glow.
What gives?
