I have one of those. Along with "Designing Great Beers" it's how I make all of my recipes. Don't knock it till you've tried it. Who needs an Ipad or a PC on brewday? I brew analog beer.
When they make it with a circuit board, silicon chips, a hard drive and LCD screen I would be interested. Oh wait! I already have one of those! I'm using it right now.
Here's another slide chart - this one for balancing keg systems. I collect slide rules, but not slide charts like this, but I had to have this one! I'm not sure just how old it is. (Sorry about the picture quality).