Very cool analysis. 
something I’ve wondered, why did the mask even need a neck extension?
I really enjoyed reading this. The 4 mask has always made me think and you did a great job classifying them! I think there should be a course offered for studying the masks 
There’s an old issue of Gorezone where they do an interview with Ken Horn about the effects and masks in Halloween 4. In there he says that they had the Kirk left over from the production of Halloween II, and that they molded that mask and made a handful more that were also used in the film. If it’s got the neck extension it’s most likely one of the recasts that were created, as shrinkage and trimming would have made the neck shorter.
You learn something new every day.
It’s news to me that the Kirk mask was even used in the fourth movie! I thought they had to use a different mask because they were not allowed to use the kirk one anymore?
Assembling screenshots and starting my draft now that I’ve settled at university… should be finished by tomorrow evening and on the site whenever Derek approves it 
Great work JDash10, nice read!