I have a Blackjack Small and a Trailguide III, and the 52100 holds an edge very well indeed. I have used my Small extensively since I got it last week, and finally got tired of waiting for it to get dull so I could try my hand at sharpening the dual convex edge.
After a week of serious use, cutting lots of thick cardboard, pipe insulation, food stuffs, plastic, vinyl tubing, and misc. fibrous materials, the edge went from incredibly hair popping sharp to extremely sharp.
Finally, today, I got tired of waiting, and stropped the Small on a loaded strop, and easily brought the edge back to scary sharp again.
As for Marbles making the knives, I myself had thought that Ken Warner was making them, but now I am confused...hopefully somebody else knows for sure.
I do know that Blackjack knives are an incredible bargain, and the Small is just outstanding, especially at $88 delivered.