To what book are you referring?
That box is really something. Took me a long time looking at the original to figure out how that hinge worked (and then, of course, I reread what you wrote and see that you actually described it, had I been paying attention instead of looking at the pretty pictures...). Do those brass rivets in the surround next to the upper corner of the lid and beside the middle screw underneath hold the release and kick springs?
Looks to me like while Fainot used a single pin for the hinge he cut away the rear of the lid knuckle in the middle, so the pin is exposed inside the lid for much of its length. Cutting away the back of the knuckle would make driving that long pin a lot easier without risking it getting bent, I guess, though it seems like just using two short pins on the ends would have been easier.
Edited to add: Fainot seems to have finished his gunsmithing career in Lancaster, PA. I wonder if he trained someone who moved out to Kentucky.