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2597609
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Patent number 2,597,609
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Issue date May 20, 1952
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G06 - COMPUTING CALCULATING COUNTING
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Patent number 2,513,491
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G06 - COMPUTING CALCULATING COUNTING
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Patent number 2,252,749
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Issue date Aug 19, 1941
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G06 - COMPUTING CALCULATING COUNTING
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2233830
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Issue date Mar 4, 1941
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G06 - COMPUTING CALCULATING COUNTING