This is an incredible Primitive Penny Rug and It uses FELT, something so popular today that the COOPER Hewitt Museum just had an exhibition around felting techniques. The backing is a flour or grain sack. All the circles and layers of circles have been sewn and resewn by hand and crude machine. It was stitched and restitched when I got it. All large overhand thick thread. The teardrop edge is very typical of this style. It belongs in a folk art collection!