I just noticed something weird when I was looking closely at the shots.
Next to the headphone jack, there's a tiny hole, that resembles the mic located in the same spot on the iPad.
as far as I know, the iPhone has to have its mic in the lower part.
or maybe, it's just a reset button?![]()
The pin hole is probably for a battery compartment release. Here's a picture I created explaining where it opens.

This explains why there is a slit beside the headphone Jack