This file is not from the image, sketch nor modeling.
This is 3D scanned from screen used 1:1 life size endo skull replica from stan winston.
And I fixed all meshes correctly with FreeForm and it is not a void but fullfilled one.
Perfect proportion, and no broken meshes, I already printed it with ZCorp RP machine.
I'm not a graphic designer, mechanical engineer, garantee the accuracy of this file.
I recommand this file for machining, don't be blinded by rendering of pure models.