Shown here is an unpainted first shot torso of Clark Kent. While not the most exciting of prototypes, it does offer a unique glimpse of how the torsos were put together.
Above, one can see that the torso splits into two pieces. A process called sonic welding is used to merge the two torso halves of a figure together during the production of the toy. Obviously, this piece was never subjected to that process. Various details are located inside of the torso to serve as attachment points or placeholders for the internal action mechanism. I think this piece offers a nice partial glimpse into the internal construction of the figure.