Micheal_3 :
it could be a factory case but their is no brand name on it whatsoever... but it is big, around over 1 half of a foot tall and deep, and it is around half a foot wide.
words like "around" are not usefull in any way shape or form.
Assuming that your eye-balling it is even half way accurate, a 1/4 of an inch could be the make or break difference so "around X" does not cut it.
Also the exterior dimensions mean absolutely nothing. If someone asks if a bed will fit inside a room you don't go and measure the outside dimensions of the house.
Power off the PC and remove the power cable for extra safety.
Remove the side cover
Take a tape measure and measure from the back slot cover on the case (where the gpu ports would be at), and measure to the first obstruction.
So for the example in the picture the first obstruction is the hard drive cage that is about at the 30cm mark on the tape measure. Naturally with the tape measure you can get an exact number.