Comment by devindotcom

How fun. I also found this when I was looking to learn a bit about how to operate a slide rule a friend gave me:

http://www.sliderule.ozmanor.com/srmanl.html

They're really interesting items and of course can be gotten for a couple bucks at any antique knick-knack shop. It's worth taking an hour or two to learn the general idea of how they work if you're curious.