Börse Stuttgart Group, the operator of Germany's second-largest stock exchange, has completed a blockchain technology test for secondary market trading in partnership with the European Central Bank (ECB). Six partner banks also took part in the test, including Commerzbank, Deutsche Bank, and DZ Bank. Using a blockchain-based settlement solution, Börse Stuttgart Group tested various transactions involving tokenized securities. The test focused on the interoperability of blockchain and central bank money. "The settlement time was reduced from the usual two days down to a few minutes," the firm said in a statement.