Norwegian ship Buesten visited the Black Sea according to a letter of the German naval attaché at Istanbul dated 17 February 1940 1940

In his letter dated Istanbul, Turkey 17 February 1940 No. 801 g. reported the German naval attaché to the Oberkommando der Wehrmacht Abteilung Ausland the neutral ships passing Istanbul coming out of the Black Sea and loaded with contraband for or chartered by the enemy. An item reported on 26 February the Norwegian ship Buesten loaded with 7,850 ton petrol going from Constanta, Romania to Gibraltar for orders.

Source

Bundesarchiv. German Marineattaché for Greece, Romania and Bulgaria 1939-1941. RM 12-II/459.