Paleo, that still could be anything from 1050 to S7!
With unknow steel you start with the gentlest quench and if that doesn't get hard enough you go harsher, Remember that you may have a decarb layer so when you check it with a file dig in a bit---I "sharpen" the tip a bit to not leave a notch but still get through any decarb.
Even if it's the correct hardness you will probably want to draw a low temper on it to make it tougher.
I'd try oil as a good general first guess (not the gentlest but the air hardening are usually high alloy top dollar metal and so not used a lot)
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Thomas
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