Hmmm... it looks like one entire wall (the bottom wall) of that thing is wide open. Probably need to cover that with something, but still a pretty good deal for 16x16x8.
The hole on the bottom of the box is for the gland plate, in the Ebay ad it says it comes with it. So no worries there.
In the pictures there are 2 different sub panels shown. One that is galvanized and the other painted orange. My recommendation would be to sand off the paint where proper grounding of the components is required.
I used that same box from them. Works great for a Kal clone. The bottom plate comes with a gasket. I used JB weld to seal it up instead of gasket. I actually used it as the top and cut it from my heat sink. Good to see them back in stock, they have been OOS for a while. Just a FYI, their regular store is much cheaper for stuff, better shipping rates. http://www.pioneerbreaker.com/
btw, mine came without the backplate, they sent one free of charge.