I don't know the original story for O1 steel, but suspect the array of German and other alloys labeled chrome vanadium were much more common and less expensive and probably still are. O1 has found some popularity with woodworking tool makers just in the last decade as well as some knife enthusiasts. The fact that McMaster Carr carries it in starred brand suggests that starrett and some others may use it to make measuring tools, and I'm sure it's used some elsewhere, but I've never seen it outside of knives, razors and tools given by spec (It doesn't make a very good razor, too much alloying in it). It's generally good for those of us whom are just amateurs because the average person can fully harden it with motor oil quench, or vegetable oil, temper it in any kitchen oven, and it won't air harden when you drill or cut it. It also doesn't turn out too bad if you just quench it quickly after a quick heat.
The various German alloys don't show up here at most metals places and they have a confusing numbering system whereas we're kind of used to a name and number combo.
The older razors are much better in a more plain alloy with just a little bit of nickel alloy, and the knife world seems to prefer 52100, which has better toughness at high hardness.
