Buck has not been using 420HC for the past "50 (+) years!" You guy standing up for Buck's use of 420HC may want to do a little research before posting.
Ask any custom knifemaker to build you an knife, with the exception of a dive knife, out of 420HC and see if they'll do it and what they tell you.

Buck puts the best possible heat treatment they can on their 420HC, but at the end of the day, 420HC still has a lower Carbon content than is recommended by any professional knifemaker for a non-maritime use, non-culinary use, cutting instrument!
Regards,
3G