Yeah, that 'milky' look might be the result of exposure to something caustic. I've seen that on some stainless blades. Same could be said for the darker splotches, which look more like what we call 'patina', but could also result from exposure to acids. Based on all of that, and the nicked-up edge, I'd say that blade had been used pretty hard.
Some sanding and/or polishing with paste compounds (Flitz, etc) might clean up the staining, so long as the blade isn't too deeply etched by whatever caustic stuff it was exposed to. If deeply etched, at least some sanding would be needed to clean it up. Being the knife is a firmly-committed user now, that may or may not be worthwhile.
Might also be worth considering a 'spa treatment' from CRK as well, if you really want it cleaned up again and the edge resharpened. I think they offer that service, maybe at some cost. But it's something to think about.
