Yoshida Hamono works with one of the hardest stainless steel commerically available. ZDP-189, manufactured by Hitachi Metals is one of the highest quality stainless steels available on the market. A powdered steel, ZDP-189 can be hardened up to 66/67 HRC, harder than all other stainless steels. Few factories have learnt how to take advantage of these ultra hard steels, but nevertheless these knives will retain their cutting edge for an extremely long time before needing to be resharpened.
Very few factories have the proficiency to work with ZDP-189 and these knives are hard to come by. ZDP-189 is difficult to sharpen, but will hold an edge for a very long time. Production of these wonderful knives is extremely limited and we are only able to be supplied with a few every year.