FRAMINGHAM (07/17/2000) - My father bought this Post VersaLog slide rule for US$22 back in 1959. At the time, his tuition at the City College of New York was $14.50 a semester, so the purchase was a significant one. To keep it in top condition, he would tune the instrument every few months, aligning the front and back hairlines with the top and bottom fixed rules, and cleaning the grooves to allow it to slide more easily.
The English mathematician William Oughtred is widely credited with inventing the slide rule, somewhere around 1630, though his work was inspired by John Napier, a Scot who in 1614 showed that by adding and subtracting logarithms, one could multiply and divide numbers. The modern slide rule, if handled correctly, can be used to multiply and divide, calculate logarithms and trigonometric functions, and figure out roots and powers. Engineers used them to build bridges, astronauts brought them on space missions, and students relied on them to pass even the toughest math and science exams. Despite its versatility, the slide rule fell out of favor in the 1970s (credit the pocket calculator), though in some circles it is still collected and even revered.
For the record, my father swears he never hung the slide rule's long leather case from his belt. Only nerds did that.