I have my father's slide rule. The slider is corroded in place though. I want clean it up and learn how to use it.
Most of the 20th Century advances were made using the Slide Rule.
After the Abacus, it is the most fundamental mathematical instrument known before the calculator.
Without it, there would be no calculator or Lunar Landing...
Think about that!
I have one from my father, dating to the 1940s in pristine condition (last time I checked).
I still have mine, and would ahve to pull it out, blow off 30 yrs of dust off it, and then try to remember how to use it without remembering all the log tables.