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-
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3813886
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Patent number 3,813,886
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Issue date Jun 4, 1974
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E21 - EARTH DRILLING MINING
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3397544
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Patent number 3,397,544
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Issue date Aug 20, 1968
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E21 - EARTH DRILLING MINING
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3186179
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Patent number 3,186,179
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Issue date Jun 1, 1965
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E21 - EARTH DRILLING MINING
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3115754
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Patent number 3,115,754
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Issue date Dec 31, 1963
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E21 - EARTH DRILLING MINING
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2795935
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Patent number 2,795,935
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Issue date Jun 18, 1957
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E21 - EARTH DRILLING MINING