To start off.
My phone came in a box which represented the black version. So although mine was white I was given a the box with the black device printed on it.
Whereas the white device had numerous stickers around it mine only had the screen protector and the camera/back stickers. My device also had an extra white charger come with it (probably Chinese, maybe American? - it was the D820 US version after all).
The box itself seemed to be legitimate with the same manuals and the same layout however (unless it was my handling/opening of the box) it turned on as I opened it.
Mine was bought from here: http://www.ebay.co.uk/itm/271642121230
So overall it SEEMED legitimate, I can provide images if neccissary however I BELIEVE it was legitimate, and I can't confirm if it was. My sim ejection tool looked similar to this: http://www.amazon.co.uk/Card-Removal-Remover-Eject-iPhone/dp/B009PJFHUK
Also if you would like any information on enabling European bands for 4g just ask (if you do decide to buy the D820 model - Americas model).