On my feather duster the decklid was all steel and I could find no evidence of it being changed at some point. But I did notice that the side glass is thinner than the standard car glass. So that was also an area of weight savings.
Well, the aluminum inner structure was part of what made the option package.
So your car had the wrong one installed at the factory or it was changed. That's the idea when making body repairs..... "no evidence of it being changed" is a perfect repair.
