ECOBRA 1611 Duplex Slide Rule
date: label: date made
content: after 1945
name: label: maker
content: Ecobra
notes: label: Description
content: This ten-inch aluminum linear duplex slide rule is coated with white enamel and has aluminum endpieces. One side of the base has scales for sin/cos, tg/ctg (tangent/cotangent), DF, D, and the square root of 1 – x<sup>2</sup> (a Pythagorean or P scale). On the slide are CF, CI, and C scales. The right end of the slide is marked: ECO BRA (/) Nr. 1611. The lower right corner of the base is marked: System (/) DARMSTADT. On the other side, the base has K, A, LL3, LL2, and LL1 scales. The slide has B, lg, and C scales. The numbers on the C, LL3, LL2, and LL1 scales are green, which is unusual. The indicator is plastic with aluminum edges. The letter Q is on the hairline on one side. On the other side, Q is on the hairline and W and PS are on shorter hairlines at the top of the indicator. These hairlines are for circle conversion and peripheral horsepower conversion, respectively.
label: Description
content: The rule fits in a cardboard box covered with maroon synthetic leather. The top edge of the box is marked No. 1611. The front is marked with the Ecobra logo, and the back is marked MADE IN GERMANY.
label: Description
content: Alwin Walther (1898–1967) of the Technische Hochschule in Darmstadt, Germany, developed the Darmstadt system of scales in 1934. His arrangement was aimed particularly at engineers. ECOBRA or Eco Bra was a brand name of Bayerische Reisszeugfabrik, a Nuremberg maker of drawing instruments that was purchased by Joseph Dietzgen in 1909. The company began producing slide rules before World War II, and after the war, Eugene Dietzgen Company of Chicago distributed ECOBRA rules in the United States. Metal rules were more popular in the United States than they were in Europe.
label: Description
content: Reference: Dieter von Jezierski, <i>Slide Rules: A Journey Through Three Centuries</i>, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 34–35, 52–53.
label: Location
content: Currently not on view
place: label: place made
content: Germany: Bavaria, Nuremberg
topic: label: Subject
content: Mathematics
label: Subject
content: Rule, Calculating
label: Subject
content: Engineering
setName: label: See more items in
content: Medicine and Science: Mathematics
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content: Science & Mathematics
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content: Slide Rules
creditLine: label: Credit Line
content: Gift of Sebastian J. Tralongo
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1984.1071.04
label: accession number
content: 1984.1071
label: catalog number
content: 1984.1071.04
objectType: label: Object Name
content: slide rule
physicalDescription: label: Physical Description
content: aluminum (overall material)
label: Physical Description
content: paper (case material)
label: Physical Description
content: synthetic leather (case material)
label: Physical Description
content: plastic (cursor material)
label: Measurements
content: overall: 1.8 cm x 33.1 cm x 6.1 cm; 23/32 in x 13 1/32 in x 2 13/32 in