What I see in those pics, is a knife that just needs a bit of TLC to get it back into nice condition. As has been said...FIRST.... check to see if their is any value in the knife/as a collector piece. ANYTHING done in the form of "clean up" can destroy the value. I've seen it happen many times over the years. Somebody comes to my shop with what was a highly valuable knife, that had been butchered with a dremel of bench grinder, asking me to "fix it". That is damage and value loss that cannot be undone.
That being said, some light hand sanding on the leather handle with 220 grit of finer, and an overnight soak in straight mineral oil will bring it back to life. It's a few days process.... after an overnight soak, you need to let the handle "drain" for a day of two atop a clean rag. Being a natural material, and subject to "moving" (meaning it will shrink and expand with environmental changes), you DO NOT want to put any type of "sealer" on it. Allow it to "breath" and it will last much longer than if a "sealer" is used. So folks dip/soak older/worn leather handles in melted beeswax.... which also works very well.
As has also been said, take your time and HAND finish/sand the blade..... any refurbishing job on a knife (if done correctly) is usually a somewhat lengthy process... and the more "elbow grease" you apply, typically the better it comes out.