If you have a heat source you might try hardening one for comparison. If no other choice, build a bonfire and look for a cherry red color. This will take a while. Then throw it in a 50 gal. drum half full of water, CAREFULLY. Depending on alloy, might work, might not. I know they are heavy, and too big to treat with a torch. Good luck, and, again, Be Very Careful. Good luck.