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Movable roof support mechanism
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Patent number 4,026,118
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Issue date May 31, 1977
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The United States of America as represented by the Secretary of the Interior
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Frank Vernon McCay
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E21 - EARTH DRILLING MINING
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Mine roof support
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Patent number 3,996,753
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Issue date Dec 14, 1976
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Becorit Grubenausbau GmbH
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Walter Lubojatsky
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E21 - EARTH DRILLING MINING
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3854293
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Patent number 3,854,293
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Issue date Dec 17, 1974
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E21 - EARTH DRILLING MINING
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3830456
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Patent number 3,830,456
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Issue date Aug 20, 1974
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E21 - EARTH DRILLING MINING
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3466875
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Patent number 3,466,875
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Issue date Sep 16, 1969
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E21 - EARTH DRILLING MINING
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3399927
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Patent number 3,399,927
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Issue date Sep 3, 1968
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E21 - EARTH DRILLING MINING
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2711634
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Patent number 2,711,634
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Issue date Jun 28, 1955
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E21 - EARTH DRILLING MINING