chalkboard vs writing board

chalkboard

noun
  • A slate or enamel board for writing on with chalk; a predecessor to a whiteboard. 

verb
  • To write or draw on a chalkboard. 

writing board

noun
  • A smooth vertical surface to be written upon using an erasable material, large enough for several persons to read simultaneously. 

How often have the words chalkboard and writing board occurred in a corpus of books? (source: Google Ngram Viewer )