I agree about it being being man made, the edges are mostly smooth, like they could have been cut with a wet saw. And most of the edge is beveled outward except for one side. Almost looks like a blank for a base for something to sit on or maybe a craft to paint on and stand on one flat side on shelf. Also the bottom is completely smooth but has several bumps that a wet saw would not have left behind. The top where you see the crease line in pic is actually a change from one thickness to another. The smaller side ( or heal of shoe ) is 1/4" thinner than larger side. Smaller side much smoother than larger side as if someone started shaving rock smooth but quit.