Ever use one of these?

This is a Keuffel & Esser slide rule, just like the one I have in a box in my closet and am too lazy to drag out and photograph.

I’ve had it since my high school days when my physics and chemistry teacher Charles Geheb taught us how to use this handy little calculating device. Serious science geeks wore one of these on a belt scabbard, just like an SA or SS dagger in the Third Reich.

The reign of the slide rule as a scientific calculating tool ended abruptly in 1972 with the introduction of the HP-35 pocket scientific calculator by Hewlett-Packard. My brother-in-law Bob Teerman was in architecture school at Purdue University at the time and had the first HP-35 I ever saw. I recognized it as the breakthrough product that it was at the time.

I’m hanging onto my old K&E slide rule out of nostalgia and the realization that it doesn’t need batteries and will still be functional if a nuclear magnetic pulse or solar storm wipes out all of our electronic devices.