The older ones like yours(and mine) were made from 425M stainless. They were about the only ones to use that steel a lot. The steel is a fairly simple stainless with .5% carbon, but it had a great heattreat, and originally a convex (moran) edge. Buck received a lot of complaints that the knife was hard to sharpen, which was true if you tried to put a conventional flat edge bevel on a convex edge. They then switched to a more conventional flat edge grind, and that apparently solved the problem. Somewhere along the way, in the last few years, Buck switched over to their 420HC steel, and a good knife went bad as far as I"m concerned.