From Jez's site:
Quote:
When making Return of the Jedi in 1981, Lucasfilm realised they needed more that the 12 remaining Stormtrooper helmets left from ANH/ESB so they made another 50 or so from the moulds of one of the remaining ANH/ESB helmets. However the mould collapsed during their manufacture, producing this distinctive squeezed and less sharp appearance.
There was also clearly a new ear cap made for most of the jedi helmets, the right one as you look at the helmets.
I seem to remember something about skins being moulded for Jedi helmets, which would account for the softer appearance.
Joe
EDIT:
Quote:
The original ANH/ESB helmet was dissembled and the pieces were back filled with Plaster of Paris, before ABS was vac formed over the top. The ABS was then used as a mould to form the new epoxy aluminium vac-form dies, from which the screen-used helmets derived.
This accounts for the softening of all the features. It also makes sense that the tears have marks in them on Jedi helmets.