Yes, 'Tru-Sharp' is 420HC. Case spec's its hardness in the HRC 55-57 range - a little less hard than Buck's 420HC (HRC 57-59). That means the burrs will be a little more ductile ('bendy') on the Case blades and will take slightly more work to clean up. The burrs on Buck's 420HC blades tend to be a bit more brittle and will break away sooner, once they're thin enough. In terms of just sharpening either of them, they feel almost indestinguishable from one another on something like an India stone (aluminum oxide), which handles both of them easily.
I've found that the slightly softer Case 420HC, because it's not quite as brittle at the edge, will tend to retain a finer, more hair-popping shaving sharpness a bit longer, so long as it's dedicated only for that sort of fine cutting - it'll tend to roll or deform more easily in heavier use at that high finish. The slightly harder Buck 420HC tends to be a little more brittle at the edge. At a higher finish, it'll be more stable for heavier work like cutting cardboard, etc. But really fine, shaving-sharp edges tend to go away more quickly on the Buck blades, even by a little too much stropping at times. But the working edge left on the Buck, after the hair-popping sharpness goes away, is more stable for heavier cutting.
And relatively narrow edge geometry, like 25° - 30° inclusive, will improve the functional (useful) edge retention in either of them. That's simply due to the thinness of the steel behind the apex, after the apex dulls a little bit. I set the edges in ALL of my knives in that range, and they hold up well in normal uses.
Most of what I carry & use these days is either or both of Case & Buck blades, in their standard 420HC stainless. So, I'm noticing these subtle differences between them all the time in use and when I touch them up.
