You are right, the bottom section is missing. Well, the camera is working fine. None of my cameras have problems before so I am taking my chance here.
The MK3 is much faster than the MK2. I am happy with the purchase.
I'm thinking of opening it as well. so far I had two 5d MK2, one 7d and xti - none of them had issues with funtionality. It's really hard to resist opening it while I have it on hand.