The first of these steels to be released was Carpenter’s CD#1 around 2004 . The “CD” stands for coining die, which is an application that benefits from high toughness. The Zapp version, Z-Tuff, came later, though both are very similar. These steels have their roots in the “Vasco Die” series of 8% Cr steels, of which CPM-3V and CPM-CruWear are a part. CPM-3V is a powder metallurgy version of Vasco Die, released by Vanadium Alloys Steel Company (Vasco) of Latrobe, Pennsylvania in the 1960s. CPM-CruWear is a powder metallurgy version of the higher carbon version, Vasco Wear. Vasco Wear had some use in knives in the 1980s, such as from knifemaker Ted Dowell and knife company Gerber. There was also a lower carbon version in this series called Vasco Tuf. You can read more about the history of these Vasco grades in this article. They all combine 8% Cr with vanadium addition for wear resistance, and are known for their good balanced properties. Vasco Die was originally advertised as combining the toughness of A2 with the wear resistance of D2, which are both popular die steels.