The shopkeeper tilts his head to the side and thinks. Hard. The struggle is pretty much written on his face as he balances the need to keep his reputation with his distaste for the things that were apparently done with the blade. In the end, he comes up with the perfect solution:
"Well, good you ain't no cops. Never seen this steel, though", - he breaks into a wide grin, - "But I know the story of a very similar dagger. Too bad my time has a price: I'm working, you know".
The man gestures to the walls cluttered with weaponry:
"How about you buy something? Then I can excuse trading tall tales: you'll tell me where you might or might not have got that blade and if I'm sympathetic I'll tell you that story that might help you".
He returns to sharpening the axe, giving them time to think.
In game mechanics terms the shopkeeper offers the Kindred to buy a blade worth Resources 2 month income or more (as long as you don't choose a chakram or something, this shop carries it). A friendly reminder: social skill rolls affect to modify the actions of other characters. Unless you roll something, the characters you are interacting with will act in their own best interests as they perceieve them. If you want the shopkeeper to tell you more than he wants to, roll Man + Persuasion. Teamwork applies (you can choose the primary actor in the OOC thread or, better, through PMs). The price of the blade you buy can be used as an equipment bonus.