I've seen fiberglass quarters for sale. I honestly can't think of what application they could possibly be used in. It doesn't even make any sense. If anybody does know what the point is I would love to know the reasoning behind it.
The fiberglass quarters were the first to show up in the aftermarket, long before Sherman or anyone else started making reproduction parts 30+ years ago. They could be had with the goofy wheel flares to cover N50's.