museum piece vs period piece

museum piece

noun
  • A very old item, especially an obsolete piece of technology. 

period piece

noun
  • A work which evokes the era in which it was produced, but may not have any other especial features. 

  • A work of art or drama which evokes a particular historical era. 

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