The research is about the painting 'Portrait of William III. of Orange-Nassau' (carried off by the french army to the Louvre in 1795, today in the Musée des Beaux Arts de Lyon), and the appendant preliminary work for this painting. Provenance of the painting with the portrait of the young Prince William: The portrait painting was a gift (Deal) to William III. of Orange-Nassau, Governor of the Netherlands in 1672, King of England, Scotland and Ireland (as William II. and "King Billy"). The concrete historical background of the order placed, a price agreement reached and much more are known. It is one of the few secured works of Jan Davidsz De Heem provenance. Information about the preparatory work: Quote: " According to the workshop practice at that time, Jan Davidsz. bequeathed countless drawings of plants to his painter's sons. He must have possessed an immense treasure trove of drawings. In this context, the absence of De Heem's certified drawings represents a peculiarity that has hardly been noticed to date ..... but one can only speculate about the fate of his study sheets" (Weltkunst 1991, Issue 11, pp. 1658/59).The preparatory work for the portrait painting is the only "document" by Jan Davidsz. De Heem, which documents a study elaboration.