indistinguishable vs of a piece

indistinguishable

noun
  • Any of a set of things that cannot be distinguished. 

adj
  • Not capable of being perceived or known. 

  • Not distinguishable; not capable of being perceived, known, or discriminated as separate and distinct 

of a piece

prep
  • Used other than figuratively or idiomatically: see of, a, piece. 

  • Of the same kind. 

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