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3812788
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Patent number 3,812,788
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Issue date May 28, 1974
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E01 - CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
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3797407
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Patent number 3,797,407
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Issue date Mar 19, 1974
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E01 - CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
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2725970
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Patent number 2,725,970
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Issue date Dec 6, 1955
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E01 - CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES