W2 was a steel that was on its way out the door. Some have expressed concerns recently that O1 may be on the outs too. In many tool applications, W2 had been replaced either by W1, O1 or one of the nominal air hardening tool steels like A2 and D2.. IIRC, the stuff that Don Hanson, Jason Knight and others found a few years back had been "out of circulation' for ten years and was leftover stock from a GM order. What has made it popular with us metal pounders is the quality of the stuff that we have, its combination of toughness and wear resistance and the fact that that it's shallow hardening makes it ideal for getting a wicked looking hamon. it also has a reputation of being a little less tempermental than O1 as far as red shortness and air hardening and 52100 in that you don't have to nail the quench right the first time. You can do it over again. The only real downside is that is can be so shallow hardening that in thicker cross sections, you can often get an "accidental hamon" where it doesn't harden through. I suspect that is not a problem in sections as thin as kitchen knives, but I will differ to my brethren who have used it in that application because I haven't made any W2 knives less than about 3/16 thick at the ricasso. Bill Moran used a lot of W2 when it was readily available and he said that it was almost as tough as 5160, had the potential to take a better edge and hold it longer. The good news is that Aldo Bruno had a batch cooked up in Germany that appears to be very similar to the round bar stock that Don Hanson has been selling and it is available in flat stock as thin as .103.