Steven, he uses different steel,
Basically the US, since they provide high quality and predictable results for heat treatment,
here is a list of steels that are used in the illustrated knife:
O-1 (Swedish)
D2 (German)
440C (German)
CPM S90V (USA)
CPM S125V (USA)
CPM 121 REX (USA)
154cm on Chef (USA)
ats-34 (Hitachi Metals Ltd.)