RC =Rockwell hardness scale I sometimes make custom knives and usually test my blades after I quench. Different steels can get harder than others, the steel in this knife is 440C, which if done correctly can get to between 54 to 59 depending on how you harden and temper the blade.
Bottom line-a blade that's harder can take a very good edge, while on the other end some people opt for a softer blade which is easy to sharpen but dulls much faster. I hope this helps. Ron