Hi Moon, you might want to check out
this thread over on on the Spyderco factory forum, gives a pretty good rundown on the various Natives.
This picture shows the four basic models.
The top one is what is know as a BRK 1st Generation Native. They were made for Blue Ridge Knives and are considered by almost everyone to be inferior to later versions. Steel on these is 440A and they have 9 thumb notches.
The second one down is a Golden made Native, a current production one in S30V, although earlier ones in 440V still show up on eBay a lot, all of them have 6 thumb notches. Mine is plain edge, but combo is also available. Oldest ones are in GIN-1, but these would only be on interest if you're looking for a collector piece.
The third is a Native II, this is the all stainless version of the Native. They have AUS-10 blades and are make in Japan. Plain edge has been discontinued, but can still found if you hunt around, combo edge is still in production.
The one on the bottom is a Native III, these too are made in Japan. They have VG-10 blades and come in plain and combo edge. The blue ones, in plain edge like mine, but without the Spyderco Forum markings on the blade, are still available from NGK, and probably elsewhere as well. Some feel the blue ones have a smoother action than the black.
Aside from the steel, the biggest differences between the regular Native and the Native III are the thickness of the handles and the clips. The Native III is considerably thicker due to the contoured handle, feels great in the hand, but does make for a bigger bulge in the pocket. As for the clips, some love the wire ones, some hate 'em. Those who love 'em say they don't scratch things up as much as the flat metal ones, them want hate 'em say they deform too easily. Me, I take both off and just carry loose in my pocket.