Damaged Helmet by ctxwing, published under Creative Commons Attribution 4.0 International license. Downloaded from SketchFab in 2018.
May have been based on Battle Damaged Sci-fi Helmet - PBR by theblueturtle_, published under a Creative Commons Attribution-NonCommercial license
The original model was built on an early draft of glTF 2.0 that did not become final. This new model has been imported and re-exported from Blender to bring it into alignment with the final release glTF 2.0 specification.