You're not gonna believe this, back in the "old days" people cut fonts out of metal. :) People still do it for fun and profit. The Blue Ox Mill in Oregon has classes on fontcutting.
I'm not a historian but this seems like the only plausible process given the technology around at the time.
I believe that the "backward-E" and later the "upside-down-A" are that way because then you did NOT need to create a new metal symbol; you could simply reuse a capital E and A and put them in upside down. I can't find a citation for this. There's other history here: https://jeff560.tripod.com/set.html