BACK STORY:
The blade has been traditionally produced using 420B (.3% carbon). Passivated to ASTM A9767-13, and HEAT TREAT AND DOUBLE TEMPER TO 50-56 Rc. AND CRYOGENIC TREAT TO -90 F OR LOWER
FOR 2 HOURS (MIN.)
420A is readily available (.2% carbon). 420B is next to impossible to find...