CPM-S90V consists of:
From Spyderco's website:
CPM-S90V is not a new steel, but it is one not commonly used in the knife industry. It is a high carbon stainless steel formerly known as CPM-420V. With 2.3% carbon it offers wicked edge retention and higher tensile strength. It has more than twice the Vanadium than CPM-S30V, providing greater wear resistance. CPM-S90V may be uncommon in our industry due to its strength, hardness and toughness; all things that can prove to be difficult in a production atmosphere. Given the extreme wear resistance, it proved to be difficult to grind, the steel didn't want to "give" or "let go" of molecules. Although frustrating in production, this characteristic speaks to what can be expected in edge retention.