I believe that anything that comes out of the original mold would be considered generation zero. “Generation” seems to indicate new molds being made off of subsequent casts, so if it’s pulled from the original mold then there would be no generational difference.
For example, if someone got their hands on the original mold for the Fett helmet, or the vacuform bucks for the armour, the results would be an identical copy, a twin of the original, aka generation zero.
T T T Talkin bout my generation...