I guessing here but If there's a wireless device it is included in the main Marvell SoC and not on the gigabyte ethernet module on the top.
Flip the board, look at a little downward from the front right corner, doesn't this look like an antenna ? (between the top corner to the crystal leg)
Flip the board, look at a little downward from the front right corner, doesn't this look like an antenna ? (between the top corner to the crystal leg)