It looks more like a summer cover for the fireplace that has been cut off. The design ends abruptly at the bottom. Is it as heavy as cast iron (which it would be if it were a fireback) or thinner and lighter, like steel or tin?

It's part of a "summer cover". They were put on after the need for fires was over, as decor and because empty fireplaces are ugly.

Thanks!

look how dirty the batts of insulation are
at the top of the fireplace.
better make sure that there is a flue
and close it when not using the fireplace!

too bad the summer cover isn't intact.
but still...its pretty.