As others have said, probably carbon tool steel, and it WILL hold an edge, in fact, it is one of the toughest tool steels there is, but it has one huge disadvantage, if it is allowed to get at all hot whilst cutting, it will immediately soften and lose the edge, so reharden it, grind it gently to sharp, touch it up with an india stone then use it with bags of coolant, and it will cut even chilled cast iron. The advantage of HSS is that it can be used almost glowing without loosing its hardness, but it is more difficult to get a perfect edge on. Remember when you heat it for hardening, you must heat to the curie point (where it stops being magnetic) and then hold it at that temp for 20 minutes per inch of thickness, so say it is 1/2" thick, keep ot above curie for 10 minutes, then quench as above, start with oil, then try water if that doesnt work. A file will tell you if you are getting there! I have got a lot of carbon steel lathe tools that I have picked up in box lots at auctions, many of them obviously made from old files, that have been softened, beaten to shape, then re-hardene. They cut!