The mesh is good in zbrush (I've had this design manufactured/cast), appears to be solid using plastic to render although there are dark spots in the areas where "holes" appear using a bronze metal, but with the metal there appear to be holes in the surface. I thought it was lighting/angle but these appear open/black regardless of how I position the camera.
Any ideas what's causing it?
No big... Gimp solved the problem.
Have you tried to calculate the normals with edit geometry?