The Stiper knives are made from D2 Steel well known for being difficult to work with but very strong.
D2 Steel Analysis:
1.5 - 1.6% Carbon 0.2% - 0.6% Silicon
0.15% - 0.45% Manganese 0.03 (max) Phosphorus
0.03 (max) Sulphur 11% Chrome
0.7% Moly 0.8% - 1.1% Vanadium