Thanks guys! Milkbaby, the 15n02 is indeed from Aldo, but I bought the 0.070" (it may have actually been 0.072"). But your observation is correct...some of the 15n20 he stocks is hard (or semi hard). Aldo told me that some of his 15n20 steel was originally slated for band saw production, and being such were already hardened/tempered and not annealed. However, IIRC, the hardness was relatively low for our knife standards, somewhere in the low to mid 40HRC. I could cut it with a hacksaw and drill it easy enough, but you could definitely tell it was semi hard. This is sort of an issue with me. I like to know exactly the condition of my steel prior to working it and heat treating. Steel "usually" comes fine spheroidized, and can go straight to hardening/quench/temper. If I don't know that for sure, then I will go through the process of normalizing it to, in layman's terms, "re-set" the structure, thermal cycle it to take care of any possible enlarged aus grain, then on to hardening operations. There is also the issue that most of Aldo's carbon steels come from the mill in Germany "heavily" (or "coarse") spheroidized. The carbon has a tight bond in it's carbide structure due to this coarse spheroidized structure, and requires a normalizing heat to free up enough carbon to get maximum hardness. At least that was the case with his steels some years back, and because of that issue, when I heat treat Aldo's carbon steels, I go through that whole rigamarole just to be safe. Aldo's early 52100 was notorious for only reaching ~63HRC post quench, and Kevin Cashen was tapped into to figure out why. Turns out it was the coarse spheroidization of the 52100, and a good normalizing heat was required in order to free the carbon from it's tight carbide hold and thus reach the goal of HRC 66-67+ post quench. I would highly recommend you do the same when working with that 15n20 you have, and any of his carbon steels. AKA: 1075, 15n20, 1084, 80CrV2, 1095, W2, 52100. (I have no idea where his O1 comes from, never used it from him). For his 15n20, normalize 1600-1650f, 10 minute soak and air cool only. Thermal cycle 3x 1500f, reduce soak times each cycle air cool only. Harden 1475f-1500f, 10 minute soak, medium or fast oil quench. 2x tempers.