Hey Alex, thanks
I guess they are not HSS but carbon steel, of some sort.
The guy's auction pages are here and he has another set similar to mine on auction at the moment here.
The steel is JIS SK4F drill rod, he says this..........
(If you don't have Japanese installed on your computer that will come out as
材質ＳＫ４Ｆ （JIS：SK4) ドリルロッド （炭素工具鋼）です。 水焼入れが可能で、刃物を製作す ることが可能です。
表面の状態は鋼材として一般的な状態です。 表面には多少の擦り傷（スジ）やシミがありま す。
That roughly translates to.......
The stuff is hard, but I'm able to get a nice SHARP edge on it.
Material SK4F (JIS: SK4) The drill rod (the carbon tool steel) is. Water hardening being possible, it is possible to produce the edged tool.
The other set he says this about.......
Maybe this would have been a better choice, but it is a bit more expensive, and I wanted to see if I could make theses tools or not.
With the free-cutting steel JIS sign SUM24L (the sulphur compound free-cutting steel) it is set. The sulphur and the lead are included, very small amount from the general sulphur free-cutting steel of SUM21/22 and the like are superior in cutting characteristic.
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
William Arthur Ward