CPM-440V (aka CPM-S60V) consists of:
Statement from Sal Glesser on the Spyderco forums:
"Spyderco was the first production company to use Crucibles particle metallurgy in production knives. I personally went to Crucible with crew to begin the project in the mid 90's. We began with S60V while is was still being called CPM 440V. We had no problem getting it hard, but in a hi 50's to low 60's it was so brittle that it would crack if dropped on concrete. We continue to experiment until we reached the conclusion that 55/56 worked best for the steel in knife blades. In the end, we dropped it. It was too hard to sharpen for customers, though edge retention was good. I don't think we would use it again." 
- The entire thread containing Mr. Glesser's comment can be found here.