Very interesting. So, basically the Supertrooper helmets could have been cast without the ear platforms and then they were later added. However the ear platforms are not identical. Do we know for sure if all of the helmets’ ears were in fact identical?
Well, obviously I'm making some assumptions but, consider this:
There's a gap between the top of the ESB left ear and the top of the red orbital band. It looks like it's about 2mm or so and you can clearly see the red in between the top of the green ear and the green of the dome.
With the PP2 the left ear meets the top of the orbital band - no trim visible and we've sufficient material in casts to know that this ear platform on the PP2 also meets the top of the band. You can see the same thing in the PP3. You get the idea.
Because it's badly damaged we have reference of what the left ear platforms of the Sandy looks like. There are several patches of missing material on the ear platform that are quite large. To me they look like what happens with unevenly applied filler; same thing happened to me when I used filler to make ear platforms.
We also know what the same ear platform looks like underneath on the ESB due to the efx stuff. Whilst some material appears to be missing, it is not the same as the Sandy missing material.
You can see similar types of missing patches on the lower RF side of the ESB ear platform. I don't have reference for the Sandy on that side.
I suspect the upper RF platform is universally cast on all six helmets but that the other platforms may have been added after, to some degree, on all of the helmets with some sort of filler type substance, probably the same type of filler that sits behind the dents.