This is the trunk inner liner. It is constructed of styrene and brass and fiberglassed for strength and appearance. The inside will be textured and finished later.
The round section at the forward edge is a separate piece that snaps on. It is the only way to install it into the frame.
The rear body section is also coming together after reworking the warp out of it… The primer is glossy; those are reflections not discoloration from sanding.
A side note, at this point it already weighs 11 ounces, that’s almost a ¾ pounder…