waynorth,
Sorry, can't ID the knife...but, if you look at the small blade, I think you can see increased activity near the tang, which corresponds with the shrinkage of the scale material. Maybe it just stopped, or maybe the knife was stored in the open position after awhile. I don't know...but I see a correlation to the discoloration and the shrinkage. JMHO.
I have used Flitz to slow the reaction, with some success.....just passing on my experience for what it might be worth.
Bill