Before I could tell them not to bother, our (lockheed) lab guys snuck a carrier plate in between shooting space shuttle parts. I cast another vote for 1010-1020 series.
They used an X-ray fluorescent (XRF) machine to determine the alloy:
http://en.wikipedia.org/wiki/X-ray_fluorescence
The reson you need to put detergent in your quenching liquid, and that you can firewalk, was discovered by this stern looking indiviual:
http://en.wikipedia.org/wiki/Leidenfrost
My edition (27) of machinery's handbook lists this series in the carburizing heat treatable alloys table at 900C (that is 1650F in christian units) follwed by plunge in water/brine with 170C/325F optional tempering. So if you want to do some mad science, and get yelled at by mom for experimenting in the kitchen (for the tempering anyhow), boldly go, the replacements are in the mail if you wreck them.
Travis