The flip side of technological advancement is obsolescence.
Light bulbs replaced oil and gas lamps. Planes, trains, and automobiles supplanted covered wagons, stagecoaches, and horse-drawn buggies. LPs succumbed to CDs, and videotapes to DVDs.
But to collectors, obsolescence has its bright side. Once manufacture of an item has ceased (except, perhaps, for reproductions), it means that a collection is potentially finite - there will be no more additions to a collector's area of interest. It also means that, over time, supply will almost certainly decrease relative to demand, and prices will rise.
The slide rule is a case in point.
Elegant in its simplicity, the slide rule was invented circa 1622 by William Oughtred, an Anglican minister, as a device for rapid calculation by the utilization of logarithmic scales. As a calculator, the slide rule reigned supreme - even traveling with the astronauts! - until the early 1970's, when it disappeared virtually overnight, replaced by increasingly inexpensive electronic calculators like the Hewlett-Packard HP-35.
Over the 350 years of its use, the slide rule was manufactured in several forms (circular, cylindrical, straight) of different materials (wood, metal, plastic, bamboo, etc.). Many had scales for specialized applications (chemistry, engineering, electronics, etc.).
There were hundreds of manufacturers. In fact, the Oughtred Society reports that an estimated "40 million slide rules were produced in the world in the 20th century alone," so it is understandable that many collectors focus on specific name brands like Keuffel and Esser (US), Pickett (US) Hemmi/"Sun" (Japan), Dennert and Pape/"Aristo" (Germany), and Faber (later Faber-Castell) (Germany).
So, just how collectible are slide rules? Prices are all over the map depending on condition, age, and rarity, from a couple of dollars for a fairly common Pickett 120ES to several hundred dollars for a Fuller's Type 2 cylindrical to several thousand dollars for an 1891 K&E 1744B, just for examples.
A specialized, precision-made metal or celluloid-coated bamboo rule of relatively limited original production will generally be much more desirable than the ubiquitous white plastic rule used by most high school students in the 1960's. A rule with its original case, manual, and box is worth more than an identical model lacking those things. And missing parts (usually the cursor) and damage (scratches, etc.) have major negative impact on value, though such rules are sometimes utilized for replacement parts.
Of course, knowledge is money in the collectibles market, so the following resources are highly recommended for those who would like to learn more about slide rules.
Websites
Eric's Slide Rule Site http://www.sliderule.ca
Informative site with downloadable manuals, tips on cleaning, links, more!
The Museum of HP Calculators http://www.hpmuseum.org/prehp.htm
Virtual museum has interesting section devoted to "early calculators" like slide rules. (Site not affiliated with the Hewlett-Packard Company.)
The Oughtred Society http://www.oughtred.org/index.shtml
International organization "dedicated to the preservation and history of slide rules and mechanical calculators." This wonderful site is a portal to all things slide rule: detailed history, copious links, patent data, more! The Society also publishes a reference manual and a twice-yearly journal.
Michele Alice is EcommerceBytes Update Contributing Editor. Michele is a freelance writer in the Berkshire mountains of Massachusetts. She collects books, science fiction memorabilia and more! Email her at makalice @ adelphia.net eBay ID: Malice9
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