Steel used in Super Banko hatchets? Re-Heat treat?

[the possum]

I picked up a neat little 14 oz Swedish Super Banko hatchet head from the bay. I've already started shaping a haft from Osage Orange for it, but when I went to start sharpening out nicks from the edge, I discovered the steel is rather soft. It's not quite as soft as fully annealed mild steel, but nowhere near what I'd want for a personal pocket axe. I'm guessing somewhere in the mid to low 40's Rc hardness. Perhaps it went through a fire?

Anyway, if I'm gonna put in all the work to make it nice, I may as well reharden it while I'm at it. I do have a small tabletop kiln that I think is big enough to fit it (still have to get it outta the garage & check), but I don't know what temp to set it at, since I don't know what kinda steel I'm dealing with. Does anyone here know what steel type they used?

 

[Hickory n steel]

No clue, but the swedish imports from the 60's-70's were the budget imports of the day and in my experience are definitely on the softer side.
The $11 Harbor freight special I had was harder than my vintage gransfors Bruks.

Not knowing any better I'd heat it past magnetic, quench it, then temper it back to a straw color like I would if making a knife from a file...etc.
I would expect that to be a perfectly adequate temper for a little hatchet like this, for a boys axe or felling axe I wouldn't even attempt it but would not expect there to be too many concerns with a little guy like this.