A 21 cm by 14 cm, 186 page, instruction manual published in 1962 by the Keuffel & Esser Co. (K&E) for their DECI-LON series of engineering-science slide rules. The slide rules, which measured 25-50 cm in length typically had eight fixed scales on the body of the device and five scales on the slider section. They were used extensively for engineering and scientific calculations with an accuracy of the order of 1 part in 2000. The use of slide rules decreased greatly around 1974 when Hewlett-Packard introduced a series of hand-held calculators that were in a price range of ~$400 CDN and hence became affordable for many. A sales brochure describing the various models of K&E accompanied the manual.
