This is a 3D export to Sketchfab where the artist has made an outline effect on the model that changes as the model is rotated. It's done by layering a copy of the model on top of the original, and enlarging the copy slightly so it's a sort of shell around the original. The faces of the copy are scaled along their normals.
THEN, the faces on the copy are reversed, so backfaces are facing out. The effect this has (on the example) is to create outlines around the model where front faces are turned to the viewer. The outlines are the thickness of the space between the faces of the original model and the offset faces of the copy. The backfaces facing the viewer are transparent (invisible) and we only see the color of the copy when the front faces are revealed as the model turns.
Long winded, I know... but here's the thing. I tried to duplicate this effect and could not get the backfaces to disappear on the copy. They render as transparent, no matter what I turn on or off in the texture panel. I tried all different combinations of interpolation but I can't get the color to disappear altogether on backfaces.