gem vs perfect example of its kind

gem

verb
  • To adorn with, or as if with, gems. 

noun
  • A type of geometrid moth, Orthonama obstipata. 

  • Any precious or highly valued thing or person. 

  • Anything of small size, or expressed within brief limits, which is regarded as a gem on account of its beauty or value, such as a small picture, a verse of poetry, or an epigram. 

  • A package containing programs or libraries for the Ruby programming language. 

  • A precious stone, usually of substantial monetary value or prized for its beauty or shine. 

perfect example of its kind

How often have the words gem and perfect example of its kind occurred in a corpus of books? (source: Google Ngram Viewer )