One of the most clever things I have ever seen done with a calculator.

[Jim Horn]

Back in the late 1970s at one of the Wescon (Western Electronics Convention and Show) events was a presentation by students competing for prizes for innovation. One presented a card reader add-on for the HP-25. Of course, I made sure to attend that! The innovation was a similar concept of having the keyboard rows and columns brought to pins of a device which would accept a classic Hollerith punched card which would be slowly pulled through by manually turning a knob which drove friction wheels to pull the card through. Each column of the card had two holes punched, one each for a row and column of the '25 keyboard which would allow those two pins to touch a conductive strip behind the punched card, thereby electrically "pressing" the corresponding key. It was as fast as the calculator and would allow loading a program into same. Of course, the resulting device was larger and more unwieldy than this one and required a keypunch machine to "program" it. But then again, it predated it by decades.