Apparently that practice still survives... https://www.harborfreight.com/magnet...two-62748.html
I learned my lesson really young. My first job was as a runner for a law firm. I did it after school from age 15 to 17. I'd just delivered some legal papers to another law firm and was parallel parked on a downtown street, reached for my keys only to realize they were still in the ignition of my locked car!!! I stood there helpless for a few minutes until I finally remembered I kept a spare key in my wallet. It was a good mistake for me to make at a young age though, because I've NEVER REPEATED that error. That horrible feeling shaped my behavior for the rest of my life! :-)

And yes, I remember having that same magnetic key box and knowing exactly where I could reach up and grab it. Not sure when I stopped using one, or why; but I used to always keep a spare key that way. Probably stopped when I got my first keyless entry system. It's all in the realm of forgotten history.