It's a phantom!!! I heard it was made from a McDonald Douglas space station concept model that was reworked. I think it was made out of some sort of foam. It was really soft. There are photos of the GJ model created for the DS9 episode TAT.
The original Douglas Aircraft Company space station was intended to be launched folded up, and unfurled in orbit. This is why the shells overlap.
Details here: Station Gallery 01
And in Another Science Fiction: Advertising the Space Race 1957-1962 by Megan Prelinger there was a reproduction of an original ad from Douglas Missile and Space Systems: