"The slide rule was all we had in my engineering days at school, as computers and battery powered calculators were just being invented, but it was surprisingly accurate. I was proud of my slide rule, as I remember paying quite a lot for it at the time with its nice leather case."
Slide rules were used by NASA engineers for years.
"And then you got a free Heavy duty Pocket Protector".
Couldn't be an engineer without a pocket protector!