Two (2) Dietzgen 1798 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 numbers 1281 and 2222 with maker's marks and model numbers, front, additional maker's marks, patent numbers and date "1933", back. Includes (2) two leather cases 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. Note: This model is depicted in the 1938 Dietzgen Catalog (see: https://www.sliderulemuseum.com/Circular/Rotarule_Dietzgen_Catalog.jpg). Provenance: Private West Tennessee Collection. CONDITION: All items in overall good condition with wear to be expected from age and manner of use. Handwritten scales in legible condition with some rubbing. Cases and manual with ink inscriptions from previous owner.