The Drunken Lizard Pub

I've reached and obtained the sword mary said I would find at her fathers house.
But, it's identified as an unknown weapon. Which is odd as Mary told me what it was and it looks awfully like a sword. Why can't I identify and use it?

Well, if you had enough skill in Lore, or a Loremaster's Ring, or a Lore spell, you probably could identify it. Otherwise, you might have to ask somebody who might be interested in buying it from you. Of course, they'll charge you...

Mary just said there was a cool weapon, by the way. I don't think she said exactly what it was. Annoying, I know. I grumped at the same discovery.