nber category 6 Others subcat 64 Earth Working & Wells

uspto classes
37 Excavating
166 Wells
171 Unearthing Plants or Buried Objects
172 Earth Working
175 Boring or Penetrating the Earth
299 Mining or In Situ Disintegration of Hard Material
405 Hydraulic and Earth Engineering
507 Earth Boring, Well Treating, and Oil Field Chemistry

Historic patent counts for subcat 64

uspto search in the 1790 to present database

ccl/37/$ OR ccl/166/$ OR ccl/171/$ OR ccl/172/$ OR ccl/175/$ OR ccl/299/$ OR ccl/405/$ OR ccl/507/$

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