Ok, I'll try. In 1980 as Buck was gearing up their new plant toward mfg. blades of the 'fine blanking' method. It was discovered that 440C eat up this tooling. Hence, they could produce more knives going to a steel such as 425M which is close to AUS8. Inclusions were noticed with this steel in the custom shop while mirror polishing. So, this was done. As demand increased another steel change was deemed in order. Thus, 420HC came on the scene. This steel offered ease of sharpening. Something Buck had heard complaints about was their blade steels were difficult to sharpen and this was a good time to address it. This could have also stemmed from folks using Arkansas stones in attempt to sharpen these wear resistant steels on. Modern, Norton stones and the advent of diamond stones has circumvented this problem. Plus, just learning how to sharpen helps. Companies make changes all the time and we can't expect trends to not be considered. I'm glad we have some choices in steels. DM