Eight (8) circular slide rulers, including Dietzgen 1798 Dempster RotaRule Model A, various Gilson models, and more. 1st item: Dietzgen 1798 Dempster RotaRule Model A 50-Inch Pocket Slide Ruler, designed and manufactured by Jack Dempster, Berkeley, California, sold by Eugene Dietzgen Company, Distributors, Chicago, New York. Comprised of two-sided round white plastic, with a transparent yellow plastic arm and scales labeled in red. Serial number 218 with maker's marks and model numbers, front, additional maker's marks, patent numbers and dated "1928", back. Includes a brown suede case with two back straps. Slide rule – 5 1/8" dia., with arm – 6" dia. Case – 5 5/8" H x 5 5/8" W x 1/4" D. 2nd item: Dietzgen 1797B Gilson Binary Slide Rule, made by Gilson Slide Rule Company, Stuart, Florida, sold by Eugene Dietzgen Company, Distributors, Chicago, New York. Comprised of a two-sided enamel coated aluminum circular disc with alternating green and yellow stripes with three transparent yellow plastic arms, two to the front, one to the back, pivoted at the center with a metal nut and bolt with metal washers on both front and back. Maker's marks front and back, dated "1940", front. Includes a red cloth and vinyl case. Slide rule – 8 3/8" dia, with longest arm – 9 1/4" dia. Case – 8 7/8" H x 9 1/2" W x 1/4" D. 3rd item: Gilson Binary Slide Rule, manufactured by Gilson Slide Rule Company, Stuart, Florida. Comprised of a two-sided white plastic disc with three transparent yellow plastic arms, two to the front, one to the back, pivoted at the center with a metal nut and bolt with metal washers on both front and back. Maker's marks front and back, dated "1940" front, dated "1931" back. Includes a tan cloth and vinyl case. Slide rule – 8 1/4" dia., with longest arm – 9" dia. 4th item: Gilson Midget Circular Slide Rule, manufactured by Gilson Slide Rule Company, Niles, Michigan. Comprised of a two-sided white plastic disc with two transparent, pivoting green plastic arms to front, pivoted at the center with a metal nut and bolt with metal washers on both front and back. Maker's marks and dated "1919", front. Includes a brown leather case. Slide rule – 4" dia., with longest arm – 4 1/2" dia. 5th item: Gilson/Tavella Midget Slide Rule, manufactured by Gilson Slide Rule Company, Stuart, Florida, and Tavella Sales Company, New York. Comprised of a two-sided white plastic disc with three transparent yellow plastic arms, two to the front, one to the back, pivoted at the center with a metal nut and bolt with metal washers on both front and back. Maker's marks front and back, dated "1936" front, dated "1931" back. Includes a black cloth and vinyl case and instruction manual housed in a black faux leather folio case with blindstamp reading "Ford" to front cover. Slide rule – 4 1/4" dia., with longest arm – 4 1/2" dia. Cases range in size from 4 3/4" H x 5" W x 3/8" D to 7" H x 5" W x 1/2" D. 6th-7th items: Two (2) Gilson Atlas Slide Rules, designed by George W. Richardson, manufactured by the Gilson Slide Rule Company, Stuart, Florida. Both comprised of two-sided paintedaluminum, with transparent yellow plastic arms, one with two to the front and two to the back and one with two to the front, one to the back, pivoted at the center with a metal nut and bolt with metal washers on both front and back. Both with maker's marks, front, one dated "1931" back. Includes one blue cloth and vinyl case. Slide rules – 8 1/4" dia., with longest arm – 9" dia. Case – 8 3/4" H x 9 1/2" W x 1/8" D. 8th item: Universal Trigonometric Combination Semi-Circular Slide Rule-Protractor Sine Table Angle Formula Finder, designed and patented by George R. Flynn, Lowell, Massachusetts, manufactured by the Whitehead & Hoag Company, Newark, New Jersey. Comprised of two off white celluloid semi-circular and circular discs with a transparent light yellow celluloid cursor, held together by a silver colored fastener. Maker's marks front and back. Includes a brown leather case with gold lettering reading "Universal Trigonometric Combination" and a snap closure. Slide rule – 6" H x 5 1/2" W. Case – 6 1/2" H x 6" W x 1/4" D. All items second quarter/mid 20th century.Provenance: Private West Tennessee Collection. CONDITION: 1st item: Wear to case. 2nd item: Wear to case. 3rd item: Wear, ink inscription from previous owner to case. 4th item: Areas of loss to edge of slide rule. Rust to nut and bolt. Back arm is missing. Wear to case. 5th item: Smallest case with wear and ink inscription from previous owner. 6th-7th items: Both with wear, loss of paint.8th item: Wear, ink inscription from previous owner to case.