Again while having a discussion with Brak's, we came to the conclusion that the ESB helmet is the only Fett helmet, from prepro to RoTJ, that has the warp in the brow. Since the ESB was vacuformed, the warp may have been caused in the construction of the helmet.
The RoTJ helmet, as you can see, does not have the brow warp. It seems quite unlikely that the ESB hero was used to create the fiberglass copies. I suppose they could have gone in and cleaned up molded copy, but I just don't think that is practical given the nature of ILM and SFX houses in general. Besides, the warp was perfectly fine for ESB, why bother to fix it now.
