Aluminium profile with inverted normals

I am stuck. Trying to use Blender's "Recalculate normals inside/outside" does not help. Whatever I do, there seem to be inverted normals. Using AccuTrans 3D and MeshLab does not reveal anything unusual to the untrained(!) eyes.

Would be happy for any help.

An additional note: I'll attach a snapshot of a view. This is an aluminium profile piece that is non-convex and has a cylindrical hole through the profile. Maybe this is impossible to get right by itself.
NB: The final object to be processed will consist of numerous of these profile pieces. The uploaded piece is a minimal test case for me.

Still hoping for some insight - or is this a question with a completely obvious answer?

--Warper

Hey warper, you might have better luck posting int he 3D design part of the forum. Folks there ask and answer a lot of questions similar to yours.

-Whystler

Hi Whystler,
I've seen some other posts by you - thanks for answering.
Did you mean to suggest another forum? It tells me "3D Design" as the forum I actually posted in!?
Warper

Hi Warper,

i took a look at your model and fixed it for you. You have to beware of the unit size though, and perhaps rescale it a bit because it doensn't meet our minimum sizes.

Hope this helps,

Cheers,

Ralph

Hi Ralph,
Thanks a lot. Even more interesting than the fixed file would be the reason for the problem and how I could have seen and fixed it myself. Anything simple like "look closer for individual inverted normals"?
EDIT: The reason for the question of course is that I want to have a model built that consists of ~30 such profile pieces. Without myself being able to fix them would be prohibitive to testing out designs.

Warper