I actually have experience using a rockwell hardness gauge myself when in a mechanical engineering classes. It will give you the rockwell hardness, but can’t identify the steel used. I would imagine a chemical analysis would be required. I tested my Benchmade McHenry marked as having 154CM steel. I am sure it was 154cm, but the hardness was lower than I expected. That knife still has the mark left by the gauge. To the best of my memory, it had a small needle like part on the gauge and hydraulic pressure was applied until the needle started moving into the metal when it would click and give the gauge reading. It would leave a very small mark. I do not know how you might test the actual metal, but would guess it might require filing and testing the shavings, but I am guessing. I know I have heard that Buck knives use of 440C with the heat treatment they used would usually result in higher rockwell hardness than other manufacturers could achieve from the same steel. In fact, I think I read they are getting 440C hardness from 420HC steel. I had a buck knife but it was lost or stolen.