Chinese steel.
Hardness varies from (usually 58-61). Most around 59 IMO.
It is not a bad steel for what it is. I feel it is similar to AUS-8. Again, JMO. Sharpens easily, doesn't hold the greatest edge, but not horrible.
Makes a good work knife or "beater" knife. The problem, is that quality varies. Makers like Kershaw and Spyderco probably do it up best.
I'd never pay a lot of money for a knife with this steel, but you can buy a pretty decent knife for a very reasonable price from some of the better makers......