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Slide rule
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Patent number 4,538,055
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Issue date Aug 27, 1985
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Harald Riehle
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G06 - COMPUTING CALCULATING COUNTING
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Planning aid
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Patent number 4,250,642
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Issue date Feb 17, 1981
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Harald Riehle
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B43 - WRITING OR DRAWING IMPLEMENTS BUREAU ACCESSORIES
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Planning device
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Patent number 4,245,401
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Issue date Jan 20, 1981
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Harald Riehle
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G09 - EDUCATION CRYPTOGRAPHY DISPLAY ADVERTISING SEALS
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Planning board
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Patent number 4,148,148
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Issue date Apr 10, 1979
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Harald Riehle
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B43 - WRITING OR DRAWING IMPLEMENTS BUREAU ACCESSORIES