It is a fake, 3G phones have usualy 2 cameras or single rotate camera, this one only have one camera in the back like the usual iPhone have. With one camera in the back of the screen it is a bit tough to do video calls.
it is defenately not a case mod cause it has a bigger screen than the current iphone and it looks like the back cover for the iphone 3G that was posted in a older thread in iClarified but it seems too plastic and cheap for an iphone... Everything in apple is becoming alluminium so the macbook will in its coming update why would it be plastic? I believe it is fake
I think this match the information on iLounge (but I am a bit skeptical), and why is the finish on the phone in the picture so worn?
https://www.iclarified.com/entry/index.php?enid=1022