I’ve seen this style before. I think you are on the right track, but I would guess it’s more like a pantograph engraving machine, which often had their own master plates using alphabet designs that have no printer’s font equivalent. One example is the Gorton, which Marcin Wichary recently researched for his similar Gorton Normal digital font.
Amaazing! I've been busy with other things and finally got the time now to read your finds. These engraved letters are very in line with the looks of Routed Gothic and National Park, which are also likely based on such origins. Thanks for the wonderful share! :)
Closest I found is PP Sans Rounded Medium, but the A and G horizontal bar is too low
