I've just taken delivery of this helmet from Australia, I've trimmed it and added a visor in photoshop for effect, but the rest is untouched. It is an alleged cast from an original screen used helmet, it certainly matches all the shots I have. I also have the RF, stalk and housing (all one resin cast) which need trimming and cleaning. The angle of my photo isn't exactly the same as the original, but it's close enough to get a good idea.
I have no intentions of making copies of this, but I am willing to share any info here on TDH (measurements, shape, size etc.)
I will show more detailed pictures over the next few days, if you have any pictures of the real helmet that you would like me to compare to then please publish them here and I'll do my best to show a shot of this helmet side by side.
A couple of immediate things that I noticed upon first inspection, the overall size is very close to the Boba Mystery Helmet (I will take proper measurements soon) and the triangles on the forehead are not as deep as Boba's.