hi. Thanks; the blade steel is 440C (which manufacturer, I don't know, was told it was from an American mill, though). Hardening temperature was 1900 degrees fahrenheit for 15 minutes; tempered at 400 degrees fahrenheit, twice, for two hours, with a zero degree cryo between the two. I did use a file guide to help me keep the plunge lines even as I could; and don't get the edges of the blade too sharp, I run mine over a contact wheel with a 150 grit belt to make sure they are blunt, don't want them chipping with the torque that get applied to them as you pry open a shell. If you make any, be sure to post and show them off! mike