Easily the coolest iPhone concept never shipped, this prototype is an octagon (!).
It seems like an iPhone 3G(S)ish prototype, given the smooth back and lack of a front-facing camera.
A smoother, rounder, smaller iPhone 4 prototype
Codenamed N90 — indicating it's an iPhone 4 design prototype — this seems like a rounder-but-smaller iPhone 4, though it's hard to tell at this scale. (Also it seems like a roadmap for how to squeeze a bigger screen into a smaller space: less bezel.)
Another potential iPhone 4 prototype
It also bears the "N90" designation, indicating it was a prototype iPhone 4 design. I like it! It's a lot like Nokia's Lumia 900, actually.
An iPod touch maybe? Or an earlier version of the above design?
Note that it has no home button at all, so I think it's an earlier version of the above design.
No Apple logo either.
The iPod mini-esque "extrusion" prototype
One thing I'd note: If those leaked new iPhone parts are real, it appears Apple's been playing with a two-toned design for some time before going all the way with it. And the Verge photos of a two-toned iPad with a kickstand to boot.
I am tripping balls over the old icon set.
This "N35" prototype seems like an old iPod touch.
It's really fat like an iPod classic, indicating it's got a hard drive, but the front is all-touchscreen. Kinda gross looking, if you ask me.
All in all, combined with the insight about the iPhone 4's original design inspiration and the decade-old iPad prototype, this week has provided one of the most revealing looks ever into Apple's design and prototyping processes — it's a real peek behind the curtain. All of these designs are very good — well, except for the iPod touch — but none of them were good enough for Apple.