We'll look forward to some pictures.
I'm sure the guys here will be able to give you a better idea, once they see it.
Oh, and I see I used some confusing language above.
What I meant to do was draw a distinction between a one-piece fiberglass dish that may have been made on a one-sided mold.
The face is smooth , but the back side may look haphazard.
I think these dishes were made with the same technology as boats, or dune-buggy bodies.
Possibly with a gun that sprays chopped up fiberglass fibers and epoxy onto a form.
The technology of the commercial dishes employs a two-sided mold.
I believe the material is a thermo-setting resin, or mold-able plastic.
The dish has very accurate and well defined edges, ribs on the back side, and is probably lighter (tbd).
Internally, they are fiberglass reinforced, but the build technology is all different.
For small sized dishes, they're one piece; for 8', 10', and 12' dishes, they're made in wedges.
I think the links I gave above should show both types.