That's some cool info, thx for sharing.it's not so much evidence of the claim but rather that is specifically what the knife makers say about kiritsuke... it is designed to combine what one can do with both an usuba and yanagiba (though not as well as either, of course). The kiritsuke design is not really that old at all... but most of the knife shapes we see today aren't that old, to be honest. Some shapes date back just a couple hundred years, while others are slightly older than that, but nothing is really that old. A lot of the shapes we see today are from towards the end of the Edo period... I feel like many people just assume they are much older than that. Some of the older shapes are crazy though. When I was in college, I wrote a thesis that covered some topics of Japanese food. In my research, I came across many older shapes and styles of knives. Deba closely resembles some, but there was much greater variety and the cross-sectional geometries were different. The Meiji jidai was when you started to see many of these things become more codified, as well as when many of the modern double bevel shapes and styles began to be made.