Confirmed:  The box will be rectangle.
I'm pretty sure it will be cuboid instead of rectangle.
		
		
	 
Unless its a solid block of atomically polished glass,it will have far more than 6 faces, so is not technically a cuboid, even a cuboid of atomically polished glass would have more than 6 faces, if the surface was magnified enough, so:
a cuboid is a mathematical concept for a shape which is physically imposable to create, due to the fact that atoms move around.
All a cuboid is is a box. 6 sides. Thats it. Don't get all microscopic saying it has more than 6 because it isn't atomically polished glass. Cuboids are everywhere and are definatly not just a mathematical concept that is impossible to create.
http://en.wikipedia.org/wiki/Cuboid
Now a perfect cuboid, that is a little different. It is impossible to prove a perfect cuboid exsists, but at the same time is is impossible to prove the non-exsistance of such a thing. Now if Craig sent the Pandora in a perfect cuboid box, that would be something to write home about.
http://en.wikipedia.org/wiki/Euler_brick#Perfect_cuboid
If the box has interior faces(can be opened), it isn't a cuboid, because the interior faces would make it have more than 6 faces in total.