There are a lot of things that are poorly documented in Randall Knife history, but the making of the Zacharias Fighter is not one of them. Bob Gaddis covers it in his book and that knife is what put Bo and Randall Made Knives on the map. That knife was made in June of 1942.
I have never seen Lt. Zacharrias' knife, but I do have photos.
When I found my Zach style fighter, I noticed the common red initials in the butt of the stag.
Recently, Wally Mabry was at the Randall Museum and took pictures of a carving knife and the but had the same red letters in the butt.
And now we have a fourth example. The 6" fighter I bought this weekend.
I arranged photos of all four knives and took a screenshot. Top is the original Zach. Then the carver in the Randall Museum, and my two knives on the bottom.
I am not sure how long Bo installed these personalizations, but it's easy to say it was close to the summer of 1942.