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United States Patent
3,448,799
Issue Date:
June 10, 1969
Current U.S. Class:
166/346
; 166/340; 166/368; 166/75.11
Current International Class:
E21B 41/10 (20060101); E21B 41/00 (20060101); E21B 43/013 (20060101); E21B 43/00 (20060101)
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