Fifty years ago, I bet Santa could barely keep up with the demand from kids clamoring for one of these under the tree. The Mathcraft Set included a slide rule, abacus, protractor, compass, and more. This kid sure looks excited to have one. Or maybe he’s wishing that Santa had brought the bug collecting kit, the weather station, or the chemical lab. All of these and more were featured in Popular Mechanics, December 1964, as good gift ideas for future scientists.

Seriously, though, the slide rule did get us to the moon.  If you want to play around with a virtual one, here are free slide rules that you can use on your Android device:

The real article, on the other hand, is getting hard to find. If you’re not careful with your Amazon search, you might wind up with one of these:

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