Having re-read this thread, it's interesting to me how the timeframe for the fighting knife development correlates with other events of the time. Lt. Zacharias (according to Gaddis) was in the 351st Searchlight Bn. This type of unit supported anti-aircraft batteries protecting the coast. The transition period from "Zach" style fighters to what we call "WW2 fighters" occurs when the 351st Bn. deployed. The entry of Jan 06, 1943, is very possibly the last day of the 351st Battalions' stay in Florida, as they sail out of the New York port of Embarkation on the 15th of Jan. 1943. If Bo had devoted much time to the Zach fighters for this unit, a lull and perhaps a chance for refinements came immediately after their departure.