Hardness of steel, angle of edge, angle of bevel, microscopic damage on the blade edge. You can't measure sharpness, and I actually doubt a Moraknife right out of the box can do that, but it's world-class steel and it will keep it's edge for years if you're nice to it.
(but you should still sharpen it quite often (if in use))
I'd say something like this might be salvageable with alot of work. i can't tell what the steel underneath that rust is like, but some sanding will probably find some nice steel somewhere underneath. The handle and guard I'd give up on though.
I'm working on two blades that were somewhere near this level of ****** up, and it's fun to make a new knife out of the remains of an old one.
Hard steel keeps an edge longer, soft steel is easier to get super sharp. Chefs use soft steel because you can get it surgically sharp super easily. That being said, hard and soft steel can both be sharpened to the same sharpness.
Now, you folks at home, I know what you're thinking. You're thinking, that can't be stag horn. It's got to be the cheaper manticore horn. But, I've got the specs right here and I'll tell you what, this is the real deal.