Reinier de Graaf (Schoonhoven, 1674 - 1717) was a son of the well-known Dutch physician Reinier de Graaf. There is no reliable indication for a relationship with the patriarch De Graeff from Amsterdam. Reinier worked as an engraver in Haarlem. Reinier de Graaf Jr. has become famous as a probable writer of the fake Rhythm of Klaas Kolijn.
The first who called De Graaf as a probable counterfeit was the Leiden professor Adriaan Kluit in a letter to Hendrik van Wijn. Kluit based his statement on the fact that Reinier de Graaf, in collaboration with the Rotterdam bookstore Pieter van Veer, had sold the rhyme chronicle manuscript for a lot of money to the scholar Cornelis van Alkemade. The Count thus benefited personally from a forgery. This does, however, raise the question whether De Graaf had sufficient expertise to create a middle-aged rhyme chronicle. The accusation of Adriaan Kluit has been widely taken over, so that one can now find the Rhythm of Klaas Kolijn on the internet under the name of Reinier de Graaf. Source
wiki
