"How did you do this"...
Sorry I didn't see this until now. I gave it a long tea bath by soaking it in a cup of boiling hot tea w/ 2 tea bags for about a day, then I dunked in a coffee bath until it darkened up a bit. You just have to experiment until you get the color you want. Its stainless so you don't have to worry about corrosion (pitting) like you do with the CV blades.
Oh, before the tea bath I also sanded the covers down a bit with 220 and then 400 grit sand paper, because I wanted the pocket warn feel and look. I think maybe that helped with the absorption of the tea. Hope that helps.