art object vs chef d'œuvre

art object

noun
  • Synonym of objet d'art (“artwork”) 

chef d'œuvre

noun
  • A work of outstanding creativity, skill or workmanship. 

  • A work created in order to qualify as a master craftsman and member of a guild. 

  • A piece of work that has been given much critical praise, especially one considered the greatest work of a person's career. 

How often have the words art object and chef d'œuvre occurred in a corpus of books? (source: Google Ngram Viewer )