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Brunsviga-Maschinewerke, Grimme, Natalis & Co., A.-G., founded in 1871, marketed the "Dupla" calculator in the 1930s for use in solving special mathematical problems, such as mechanical integration, second differences and correlation. The machine is fitted with two independent registers, one of which obtained and displayed the values of negative amounts. The second product register could be disconnected entirely while intermediate answers were obtained on the first product register. |
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