Ooooh. I don't know. The fittings on this one seem beyond the scope of restoration. They may clean up a bit, but that rust and oxidation is pretty deep and appears to be much more significant that surface corrosion.
The grip ferrule is beyond repair so that would need to be replaced. The crossguard may come along with some heavy rust remover like naval jelly but even then, it's going to be left with some significant pock marks. The scabbard looks to be the best candidate for restoration. How's the pommel cap?
Perssonally, i'd pass on this one. This is beyond the "project" level for a piece. If the dagger is a steal, like $50 or something like that, take her and just keep her as a "been there" looking piece. The other option, and I know this is blasphamy, is to buy it, and part it out as such. The blade appears to be OK, the grip looks good, and the scabbard could probably be restored. The crossguard is about dead, and I suspect as is the pommel. If the seller want $300, tell him to pound sand.
This one needs a little more than just some Semichrome and Renwax
