Originally Posted by MillionsKnives
First thing, get some 'Barkeepers friend' or 'Flitz' and get that rust off ASAP. Rust grows out of control. If it gets deep enough and pits, then the knife will have problems later. Sharpen up high enough and you'll see a big hole where the rust ate through.
Barkeepers friend works fast because of the acid in it and while good on stainless I find it to cause yellowing spots later on carbon steel if you just wash and dry.
You have to wash, scrub with baking soda paste, and wash again.
I've seen this time and again restoring old carbon steel blades.
I use Bon Ami and reserve BKF for specific needs.
For the OP that knife needs to be done a certain way so either send it someone familiar with Japanese knives or if you have waterstones watch the videos Jon Broida of Japanese Knife Imports made regarding single bevel knives before hitting a stone.
I don't see any signs of abuse shy of the rusting which looks mile to moderate and any pitting may be small.
If the blade surface feels like sandpaper you have major rust and will have bad pitting.
The handle looks remarkably clean so perhaps this spent years in storage and not used much.
It is a great find and a comparable knife is going to be $100+