Yes, the scabbard was blued. As luftpirate said, the scabbards can turn brown over time. Do not restore it, leave it as it is. Do as Andy says, just apply oil to all metal surfaces. Do not use any type of abrasives i.e. steel wool, sandpaper, wire brush etc. or chemicals. A soft cloth ( an old white T-shirt works well) and a light gun oil will work. Apply the oil let it sit a little while, then wipe excess oil off. Go gently, you do not want to remove any patina. Patina always looks better than shiny bare metal on an S84/98 III bayonet. If rust is present, the oil and cloth will remove a lot of it. I suggested using a white cloth so that you can see what is coming off. Rust will adhere to the cloth, so you need to turn the cloth to a clean spot when you see build up. Rust can act as an abrasive and remove blue or even scratch the metal. You may have to repeat oiling and wiping a few times. If you have really bad rust or corrosion, you can use extra fine brass or bronze wool to remove rust. Just go easy and take your time. Always wear cotton or Nitril gloves when you handle your bayonet. The acid in the oils on your fingers and hands can damage the blue. It doesn`t take long to do it either and can etch permanent fingerprints on the blue. And, as Andy said, we need pictures to see what is really going on.