What is "planer" steel?

[VolundoftheForge]

I was recently discussing a custom japanese tanto with an acquaintance of mine, and it's made of "planer" steel. Does anyone know what it likely is? I wish the maker would've listed what steel it actually was(Though I think he just forged out a planer).

 

[Bigfatts]

I've seen a few different tantos forged out of planer blades. Couldn't say what type of steel they actually are.

 

[co556guy]

probably something really high carbon..........

 

[kreole]

I think O1 is used a bit

 

[FortyTwoBlades]

O1 or A-2 seem to be often used for planer blades.

 

[VolundoftheForge]

O1 or A-2 seem to be often used for planer blades.

I'm hoping A2 then, not a huge fan of O1