This is something I first assumed was a very early typewriter or printing press, from the Bavarian State Library’s copy of Bellicorum instrumentorum liber cum figuris et fictitys litoris conscriptus, a collection of war machines, proto-robots and siege engines, fountains and pumps, lifting and transporting machines, defensive towers, dredges, combination locks, battering rams, a “rocket-powered” craft, the first ever depiction of the magic lantern, scaling ladders, alchemical furnaces, clockwork, robotic automata, and measuring instruments designed by Venetian engineer, physician and magus Giovanni “Johannes” de Fontana. The captions of his book are all partially in code. I now think, after reading a bit on Jeremy Norman’s History of Information site, that this thing is probably not putting the letters on paper, but using them to keep something precious safe.