Ask HN: What is the oldest (retro) machine that you still use in production?

I'm just curious to see which old machines you use regularly, either in an office, like the Commodore which powers an auto shop [1], or George R R Martin's DOS computer with WordStar [2].

Why do you keep using it? Which are the benefits? Why don't you use an emulator and retire it?

[1]: http://www.geek.com/tech/a-commodore-64-has-helped-run-an-auto-shop-for-25-years-1672510/

[2]: http://www.rollingstone.com/movies/videos/george-r-r-martin-tells-conan-his-secret-weapon-a-dos-computer-20140514