After the Second World War, investigations were carried out in various countries into what the role of the baron had been. The Zandvoort police commissioner informed the Head of the National Security Bureau that the baron was a very shady figure and that his role was not yet over. However, no concrete matters were mentioned. Much attention was paid in the report to those with whom the baron had been in contact in Zandvoort. He mentioned the German consul living on Boulevard Paulus Loot, Alfred Edgar Jung, and other German individuals.
The Central Asset Investigation Service conducted an investigation into enemy assets at the N.V. Internationale Kunstvereniging and the N.V. von der Heydt’s Bank. Despite extensive research, a correct insight into the millions of transactions was never obtained. “The impression was that most of the names appearing in the books were fictitious. It appeared that the transactions on behalf of former Emperor Wilhelm II were recorded under the name of Hauptmann Blum.”
In Switzerland, the baron was indicted, but due to a lack of evidence, an acquittal followed in that country. The Swiss authorities only took action at the insistence of the American secret service, and it is claimed that the acquittal in Switzerland at the time took place in the higher interest of Switzerland.
In 1948, the American government seized all his American bank balances and loaned artworks as enemy property.