Back to Hasiya.
I have wondered how hard it must be to forge this tool. I tend to think (Play-Dough experience) if you pound one side of a stip of steel repeatedly to form an edge eventually you end up with an edge on the outside of the curvature of the bend much like a Katana (disreguarding quenching). In this case these tools are formed counter to what the steel wants to do naturally. You would get compression and thickening on inside (edge), extension and thinning on the outside (spine). I would love to see how the Kamis forge this piece because it is exactly opposite of what the material wants to do. Do they start out with a super thick spine because it would be constantly thinning as you try to bend the steel around the edge. Does anyone follow what i'm saying?