postcard vs visiting card

postcard

noun
  • A rectangular piece of thick paper or thin cardboard intended to be written on and mailed without an envelope. In the case of a picture postcard one side carries a picture or photograph. 

verb
  • To send by means of a postcard. 

  • To send a postcard to. 

visiting card

noun
  • A written card which identifies the bearer, presented for introduction when attending a business meeting or formal social gathering. 

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