DIFF Main Group
E21B 31/00 Fishing for or freeing objects in boreholes or wells
Introduced: September 1968
Of 9 combined children, 5 exist in both systems.
4 codes are CPC-only extensions.
Child Classifications
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- E21B 31/107 using impact means for releasing stuck parts, e.g. jars since 1980 +1 CPC IPC+CPC Available in IPC and CPC