Cool Beans.

Yeah, I believe it's a KJ Eriksson 731 (if it has the 5.75 inch blade)

When you use vinegar on carbon steel blades and leave it there you're actually causing the metal to oxidize. That's most likely the patina you're seeing on the blade. This "dark rust" protects the steel and is pretty durable, as opposed to "red rust". However, I've heard it mentioned that you still want to oil the knife to stabilize the process.

I hope I got that right... I read about it in a knife forum for chefs, and it's how I started treating my carbon steel puukos and moras. It seems to jibe. In any case, if I've got that wrong, please someone let me know so I can protect my babies! <img src="/images/graemlins/smile.gif" alt="" />

On a side note: Apparently, quite a few chefs across the country, those who were able to use carbon steel blades elsewhere, are bitter that they can't legally use carbon steel knives in their current kitchens due to health codes... Bummer... <img src="/images/graemlins/grin.gif" alt="" />

Regarding a sheath, you might also check the OMG Forums. There have been a couple of threads over there about leather sheaths with fire steel holders on them.