Discolored blade?
 

Here is a dagger I just won on eBay. It appears to have a strangely discolored blade. However, the bidding was fairly low and so I figured, I'll give it a shot. I am curious what could be the cause of this discoloration (my guess is either a fire or a chemical), and most importantly, how can I remove it. The pictures are straight from the listing

Nice little knife Stan. You will probably have to wait til it arrives to see what is on the blade.Could be nothing more than some some sort of gunk fron the inside of the scabbard.
Regards Stu

You are right, I should wait until I am able to personally examine the item. However, other than the tip of the blade, it does not look like an old oil resedue (a. k. a. "Gunk"). If you look at the area from the hilt to approximately middle of the blade, you will see what appears to be a black oxidation. This is what concerns me the most...