We spot what looks like three additional thermal pads lining the back case. However...

X-rays reveal that each pad sits atop a clean cut through the steel case lining. The only reason we know of for doing that is RF pass-through.

Furthermore, each pad is connected via a flex cable to a complex antenna bus.

We're not 100% sure what we're looking at, but it seems likely this is our first peek at some ultra wideband antenna hardware.