The HD(2) moniker represents the second generation of steel in the HD line. EVERY knife in the HD line is currently forged with current elemental proportions which are slightly different then the first proprietary blend. This was done in hopes to extend edge retention, and as someone who has both blends, old HD's & new HD's, they achieved their goal.
These are not two separate lines; they are the same. It is analogous to a new model year of a car. Just because a Model T has a new engine putting out 15 more horsepower this year... its still a Model T.
This is the link to the Konosuke Wa-Honesuki in the latest blend of HD steel... the second generation of HD steel.. aka HD2 steel. http://www.chefknivestogo.com/kohd15wa.html