If you’re at all mechanically minded, you’re going to start our sort of underwhelmed, since the solution seems pretty transparent: Any determined craftsman could get similar results with a homebrew pantograph and template (hell, you could do it in LEGO).
But keep watching. You’ll get more impressed around the 2-minute mark when you see the mechanism, and more so around 2:40 when you see the cams and realize that the device isn’t tracing letterforms, but rather, in a mechanical sense, understands a series of modular strokes than can be built up in different arrangements to form different letters. Finally, you’ll totally shit yourself at 3:55 because this damned thing—built in the late 1700s—was programmable.
0.o
Absolutely stunning.