hallmark vs monoprint

hallmark

noun
  • An official marking made by a trusted party, usually an assay office, on items made of precious metals. 

  • A distinguishing characteristic. 

verb
  • To provide or stamp with a hallmark. 

monoprint

noun
  • A form of printing on paper from a glass sheet to which oil paint has been applied; monotype. 

verb
  • To print using this technique. 

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