The original Test Team model had a flat grind with differential heat treating. That means that the edge area was tempered harder than the rest of the blade. This is sometimes done with some steels to make the rest of the blade less brittle and less likely to break when used in hard impact. It is often done with swords which receive a lot of shock and impact forces. It is also more costly to do than a through-tempered blade of uniform hardness. With the increased strength of the saber grind on the new Regulator, and after testing, it was determined that differential tempering was not necessary on the Regulator, reducing the cost of the knife. So the new Reg and Dereg are through tempered. As thick as these blades are, I wouldn't worry about it. It does not affect edge holding or cutting performance. You will likely never know the difference. In fact, the new through-tempered Regulators out performed the flat ground TT models in chopping tests, probably due to the heavier blade on the new saber grind.