Flat shaded normals, have weird shading artifacts I've been working in blender for the past 3 years and never encountered something like this. When I set the normal shading for this object to flat, it shows up like this. 



I made sure the the faces all had the same normals. I tried shading them smoothly and adding sharp edges, that results in the strange smooth normal shading shown below.



Any help would be appreciated.
TL:DR press Set From Faces in the Shading tab of the Tool Shelf.

What's happened is your normals have got bent out of shape in a weird way that the usual Ctrl + N make normals consistent doesn't see as a problem.

They're all facing the right way vis-a-vis inside/outside, but they're all over the place in terms of direction. So you just tell Blender it needs to force all normals to be perpendicular to their corresponding face.

I still have no idea how this problem occurs in the first place, though. It foxed me for a good few days.