Otto Wacker (1898–1970) was a German art dealer who became infamous for commissioning and selling forgeries of paintings by Vincent van Gogh.
It was organized to coincide with the publication of de la Faille's standard catalogue of Van Gogh's work.
When Wacker delivered the last four paintings, Grete Ring [de] and Walter Feilchenfeldt, the general managers of the exhibition, noticed the differences and recognized them as fakes.
[5] In December 1928 the Matthiesen gallery, with the aid of the Federation of German Art and Antique Dealers, sued Wacker.
De la Faille responded to the accusations by publishing a supplement to his catalogue in November 1928, which listed all the paintings supplied by Wacker as fakes.
[3] The National Gallery in Berlin analysed the paints used in the seized artworks; they discovered the presence of a resin used to accelerate the drying process, which had not been found in any genuine van Goghs.
Vincent Willem van Gogh, nephew of the painter, gave the first evidence at the trial and stated that family records did not include any Russian who would have purchased any paintings.