With all being discussed about 2 holes and 3 holes, in the 1962 catalog, the photos are shown with 3 holes. These are ricasso stamped solingen blades. Perhaps the question is, if Bo had established and drilled 2 holes in earlier 1950's knives, why were these offered with 3 holes? Left over 3 holes that they didn't want to use that were pre drilled in Germany? I could see why. If Bo had decided to change to 2 hole, he could've notified Solingen to change to new 2 hole pattern, or cease drilling them, then put all the 3 hole Solingens in the bin for a later use. In this case, the M14 kit knives. Just a theory.
The blades in the 1962 catalog are ricasso stamped.
Note** The knives from Hunts book were made in 1965 and have the etched stamp out on the blade, indicating that next batch Jack was referring to.