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-
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2893679
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Patent number 2,893,679
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Issue date Jul 7, 1959
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E21 - EARTH DRILLING MINING
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2208885
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Patent number 2,208,885
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Issue date Jul 23, 1940
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E21 - EARTH DRILLING MINING
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1979503
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Patent number 1,979,503
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Issue date Nov 6, 1934
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E21 - EARTH DRILLING MINING
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1921542
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Patent number 1,921,542
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Issue date Aug 8, 1933
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E21 - EARTH DRILLING MINING
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1818633
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Patent number 1,818,633
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Issue date Aug 11, 1931
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E21 - EARTH DRILLING MINING
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1714024
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Patent number 1,714,024
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Issue date May 21, 1929
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E21 - EARTH DRILLING MINING