obverse vs superficies

obverse

noun
  • The heads side of a coin, or the side of a medal or badge that has the principal design. 

  • A proposition obtained by obversion, e.g. All men are mortal => No man is immortal. 

adj
  • Corresponding; complementary. 

  • Having the base, or end next to the attachment, narrower than the top. 

  • Turned or facing toward the observer. 

superficies

noun
  • The visible, external surface of a body. 

  • The area of a two-dimensional surface. 

  • The surface (of something immaterial, especially of the mind or soul). 

  • A building intimately associated with the land on which it is built. 

How often have the words obverse and superficies occurred in a corpus of books? (source: Google Ngram Viewer )