They aren't hamons though! The effect comes from the martensitic stainless steel sucking
carbon from the high carbon core in different layers. I got to hear Burt talk about how to
make these a couple of years ago at Ashokan. Also got to handle a couple. I just love this
effect.
It's also very tricky to do. The weld must happen in an oxygen free atmosphere with just
one chance to weld per billet. If any part doesn't weld the first time the stainless will
form an oxide barrier inside the billet that will never weld.