On a typical homburg, I've heard the upturned edge of the brim referred to as a pencil curl. What about when the edge is truly curled, where it looks like it really was molded around a torus (aka doughnut) shape? I've seen this mostly on panama and other woven hat types, on instances when the brim is fairly wide. I'm guessing that the purpose of this curl is to improve the stiffness of the brim. Is there a name for this brim curl?