Okay, I'm back. Found a cafe and pulled out a laptop, so I can address the topic a bit more.
The origins of the helmet are among various threads here on RPF but moreso on The Prop Den. I developed more than one dome and mask in parallel and there was various back-and-forth test scenarios across more than one thread to see which dome optimally fit which mask, so keeping track might be difficult. Thus here is a consolidated but shortened synopsis.
A friend acquired a flawed GH ANH casting, and Ghost Host provided a face transplant piece. He lacked the bandwidth to affect a restoration, but the project was too interesting for me to ignore, so I acquired it.
I removed the warped area and fit the face transplant donor piece:
The result of the restoration:

Making this shape-accurate would be a challenge. The rear was pulled out, creating a very large look in relation to the face which has already lost signifant material for whatever reason back in its theorized original days at Don Post Studios.
Ghost Host uses a very high quality fiberglass that is remarkably heat-resistant and difficult to cut into. For me to rearchitect the head, I had to cut this into pieces - neck, side of head, etc. and to rejoin them in order to reestablish and recontour surfaces to the right shape. I consider this move a "nightmare scenario" because there is no easy way of doing this. In certain cases, the original pieces only serve as armature for the new material (white), otherwise the surfaces would not be continuous.
What made this fun for me was being able to theorize what was sanded by Don Post Studios before the casting entered the fandom. Years back, RKW documented 8 features that cause the GH/Fiberdyne lineage masks:
http://i18.photobucket.com/albums/b138/csmaclaren/Vader/GhostHost/GHErrorsbyRKW-1.jpg
My "Dr. Jones" exercise then was to study what I had and extrapolate what was lost, similar to how a forensic artist would apply clay to a skull to rebuild muscle, tissue and skin to create a theoretical look of what the original owner might have looked like when alive. Can I do that with this - and yet sculpt in some US mold traits? (More on this later).
My faceplate reconstruction work included resculpting 17 features of the face. In addition, the tubes are brand new, and the sides and back of head were significantly rebuilt.
I'm pleased that the final result is night and day. I had also studied subtleties of masks from the US mold vs UK mold and had identified some character traits among helmets such as the MP and DJ (that came from the US mold) that I could identify even in the ESB Promo Poster Vader (which is an ANH configuration) and so I began to factor some of these traits in, as opposed to UK castings such as the TM, VP, TD and 20th Century. Thus I wanted to have some fun going the US mold direction. All this work preceded the eFX ANH and before I even knew who Rick Baker was.
The face, as you can see, is a lot fuller, and by comparison moreso than a 20th Century or Don Post Deluxe. That, in conjunction with bookface's paintwork, gives that "movie look" I've craved when I started in this hobby 2005-2006 (losing track now) but never truly understood how to recreate working with vendor kits.
So that's the mask, in a nutshell. The dome is a remastered Don Post Classic Action, but a highly flawed cast gone wrong, and it looked like straw, so I called that the "straw hat". Both WIP threads of mask and dome are fully documented here on RPF and perhaps moreso on The Prop Den.
So yes, I present to you the resurrected Quasimodo project from a while back! Originally I had this shipped to a friend who was going to mold and cast this, but he got buried with his job so it sat in his garage for the last few years gathering dust.
I'm so glad you guys enjoy it, and thank you so much for the kind words and support! Bookface will have new photos in 2-3 days.