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-
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2302034
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Patent number 2,302,034
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Issue date Nov 17, 1942
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E21 - EARTH DRILLING MINING
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2091405
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Patent number 2,091,405
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Issue date Aug 31, 1937
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E21 - EARTH DRILLING MINING
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1808224
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Patent number 1,808,224
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Issue date Jun 2, 1931
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E21 - EARTH DRILLING MINING
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1785196
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Patent number 1,785,196
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Issue date Dec 16, 1930
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E21 - EARTH DRILLING MINING
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1659923
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Patent number 1,659,923
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Issue date Feb 21, 1928
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E21 - EARTH DRILLING MINING
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1652529
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Patent number 1,652,529
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Issue date Dec 13, 1927
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E21 - EARTH DRILLING MINING
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1642182
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Patent number 1,642,182
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Issue date Sep 13, 1927
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E21 - EARTH DRILLING MINING
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1596435
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Patent number 1,596,435
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Issue date Aug 17, 1926
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E21 - EARTH DRILLING MINING
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1521022
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Patent number 1,521,022
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Issue date Dec 30, 1924
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E21 - EARTH DRILLING MINING