I took the CPM-M4 Mule out for it's first test drive on a deer hunting trip recently. It performed superbly on the game handling activities. That's the positive feedback. Unfortunately, the blade is permanently stained after only being in use for about 2 hours before being cleaned up in hot soapy water and then oiling it. When I got home I took some Flitz to it, but it still didn't clean up. I'm quite surprised by this and disappointed. Not sure if it is the steel chemistry, the finish, or both that caused it but it's pretty bad. I'll post pics soon.
It's still a perfectly serviceable knife and it will be perfectly good for the same use in the future. However, I would not have created a hunter out of this Mule if I had known the steel would stain so easily.