Very Rare Dempster RotaRule Model AA 50-Inch Pocket Slide Rulers, designed and manufactured by Jack Dempster, Berkeley, California, sold by Eugene Dietzgen Company, Distributors, Chicago, New York. Comprised of two-sided round white plastic, front scales: K A D ( C CI CIF S CS ST T CT G B F/i ), back scales: 1-100 in 4 circles DLL V2 ( V1 1-100 in 4 circles LL3 LL2 LL1 LL% L ), with a clear plastic cursor and 27 handwritten scales labeled in red. Serial number 2067 with maker's mark and model number, front, additional maker's marks, patent numbers and date "1933", back. Includes 1 leather case with snap closures and two back straps, and one (1) instruction manual. Slide Ruler – 5 1/4" dia., with cursor – 6" dia. Cases – 6" H x 5 5/8" W x 1/2" D. Manual – 7 7/8" H x 5 1/4" W x 1/8" D. Second quarter 20th century. The manual has some ware and the staples look to have corrosion making a few pages come loose as seen in the pictures. Please message me with any other questions.

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