In 1928, just before the opening of a major Van Gogh exhibition in the Kunstsalon Paul Cassirer in Berlin, the art dealer Otto Wacker supplied four additional paintings. Although they had previously been recognised as authentic by established experts, the curators, Grete Ring (1887–1952) and Walter Feilchenfeldt questioned their authenticity. Ring and Feilchenfeldt withdrew the four paintings, and the case soon developed into one of the most notorious forgery scandals of the period. Further research showed that thirty-three disputed Van Gogh paintings could be traced back to Otto Wacker, including works that had previously been described in catalogues as either…