The three day rule and dating
Even then, some manufacturers recycled their serial numbers over time, and the stock could have been left on a shelf for a period of time before the slide rule was assembled and shipped. Combined Large 6.47MB Most Keufel & Esser slide rules had serial numbers, but unfortunately they reused their 6-digit serial numbers several times.
Catalogs are an excellent indication of when a model was produced or discontinued. This chart was developed by Ed Chamberlain to help determine the date of manufacture, but one must first zero in on which period the slide rule was made.
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Dating a slide rule becomes difficult if a manufacturer did not imprinting a date code or serial number on the stock. This comprehensive research will enable you to find the period of manufacture for most every Dietzgen slide rule from 1887 through 1972.The 2-hour-plus seminar consists of tips for texting and Facebook, dating after divorce, makeovers, success stories, Rules and non-Rules celebrity relationships, Q&A, and much more.Listen on your i Phone while you drive or work out!Other Slide Rule dates are currently in development. Please refer to the museum library and individual galleries as this page is being built. Serial numbers can be used to approximate the manufacture date of a given rule however not necessarily the sales date.Found on manuals and other slide rule ephemera: 1909 - Copyright Act on published works passed by Congress. 1951 - 3 digit Area Codes in Phone numbers implemented by AT&T (Developed in 1947). 1897 New York Blueprint Paper is founded by Charles Bruning in January. The common rules were produced in regular batches but the specialty rules did not sell as well and a given batch of rules might stretch over several years.