Found this on a site that sells Chef's knives:
"HAP40 is a semi stainless, powdered high speed steel (HSS) that takes and holds an edge better than any other steel available on our site. HAP40 is fine-grained enough to sharpen very well and rates 64-68 on the Rockwell Hardness Test (HRC)even harder than the traditional carbon steels used for knives. We have specified a hardness of 65-66 HRC for our blades. Unlike other HSS steels, it can be relatively easily sharpened on normal waterstones, if not quite as easily as traditional carbon steels.
We think HAP40 holds the potential to become one of the best steels on the market for the production of high quality, high durability kitchen knives."
I will be getting an Endura for sure!