Norbert Landsteiner wrote up a post about something that’s retro-technology-typography-nerdy beyond even my usual limits and understanding: a thorough explication and an interactive demo of how the late-1940s IBM 026 key punch (the typewriter keyboard/workstation machine that operators would use to poke the holes in the computer program punchcards of that era) was able to also print tiny human-readable letters and words at the top of the cards for easy reference.
Basically IBM encoded the alphabet and other special characters onto a clever postage stamp-sized print head that would run along the top of the punchcard, with wires to each “dot” enabling the printing of each encoded character in turn, effectively an early dot-matrix printer. (it’s not easy to see, but if you squint at the image you’ll see that the red dots form the “A” character, upside-down — you’ll see it more easily if you play with the demo and choose other characters)