calling card vs postcard

calling card

noun
  • A small printed card which identifies the bearer, traditionally presented for introduction when making a social visit to a home or when attending a formal social event or business meeting. 

  • A card advertising the services of a prostitute. 

  • Excrement, especially of a domestic animal. 

  • An attribute, symptom, object, or behavior which is distinctly characteristic of someone or something. 

  • A phonecard. 

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. 

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