It's S7 tool steel that's undergone a special, SY-proprietary heat treat process. It's a general-purpose, air hardened, tool steel with a high resistance to impact and shock.

Element Percentage
Carbon 0.50%
Manganese 0.70%
Silicon 0.30%
Chromium 3.25%
Molybdenum 1.40%

Temp in DegF, Rockwell C Hardness
As Hardened - 59-61
300 - 57-59
400 - 55-57
500 - 53-55
600 - 52-54
700 - 51-53
800 - 51-53
900 - 51-53
1000 - 50-52
1100 - 43-48
1200 - 37-40