There have been quilts on this site made like that and they called them TATW. I have made lots of quilts like that that were called biscuit quilts and stuffed with polyester fiber fil. They are somewhat heavy, compared to regular quilts. I made most of mine in the Irish Chain design.
I would have guessed they were stuffed with cotton, as in cotton batting.
It is beautiful and a real treasure, I would use it for decoration and not take even one stitch out of it. Just me.