Haha, yeah I read that in another thread. I don't see it as a button though. I see it as a globe. I have an old world globe that has the exact same proportions as your avatar. It's a round globe with the same outer ring, and sits on a base.
I think if it were a button, the light source would have to be more consistent across the whole image... like this:
The original image seems to be a perfect sphere, reflecting the light in a normal fashion, but the outer ring appears to be angled, with the left side slightly forward, and the right side pushed back into the darkness.
I see the sphere suspended within the outer ring, perhaps by a pin at the top and bottom, much like an old world globe on a base:
In theory, one could use the rotate feature to rotate the outer ring a little, giving it a more three dimensional perspective. I tried that this morning and it works quite nicely. You just have to split the sphere in half, so that you can cover the back side of the ring with the second half. I don't really think it needs it though.