Dagr,
There is active rust on the blade and the scabbard that should be stopped. The purists here will suggest you buy a can of Renaissance Wax which is a museum conservators wax. Good stuff but $17.00 or more for a can. Any paste wax will do in a pinch. Add a light coat, gently polish it off then do it again. Ang again. You will be surprised the crap that comes off on the rag!
Second point is that the 'patina' is most likely nicotine. I am guessing that the The dagger was hung on a wall of someone who smoked. They also left it on the wall while painting with white paint ... you can see the splatter at the top of the grip.
