I have an old '4-dot' Buck 112 in 425M. I haven't noticed anything particularly distinctive about the steel, as compared to newer 420HC blades from Buck. I have heard some mention from one of the Buck experts here on BF, that some of Buck's 425M blades might've had 'inclusions' in the steel, i.e., some impurities of some sort, which sometimes affected their ability to sharpen up to a fine edge (inclusions break/fracture out). That might've had something to do with why they didn't stick with this steel very long, in their knives. However, I haven't seen anything specific to indicate that's happened with my 112, which seems to sharpen up OK.
I think the thing to consider most, in comparing Buck's older blades versus modern ones in 420HC, is the grind of the blade itself. Buck's older blades in 440C and 425M had thicker grinds near the edge. Gettting them to cut & slice effortlessly involves a lot of thinning out; I've done this with two of mine, including an old '2-dot' in 440C and the 4-dot in 425M. Since about ~ 2000 or so, Buck has adopted a new spec for their blade/edge grinds; I think it's called 'Edge2000' or something to that effect. They've thinned it out, both behind and at the edge to a target spec of 26°-32° inclusive, which has greatly improved cutting performance. To me, that's had the greater impact on the attractiveness of their blades, versus their steel type or even the heat treat. They come very sharp out of the box, and are much, much easier to maintain sharp, thanks to the improved grind.
David
