Teletype Model 28
The Teletype Model 28 printing mechanism is a thing of technical beauty. It's the clumination of Teletype's design efforts, and you can see that they learned a lot of lessons with their previous designs. Teletype produced a few models after the 28, but with the rise of computers, the level of mechanical complexity was never repeated.
A closeup of part of the typebox positioning mechanism. I haven't cleaned this printing unit up yet:
An overall view of the printer unit: