British tanker Conrado visited the Black Sea according to a letter of the German naval attaché at Istanbul dated 17 February 1940

In his letter dated Istanbul, Turkey 17 February 1940 No. 758 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 thet British tanker Conrado of the Eagle Oil Shipping Co. Ltd., Liverpool, England was armed with 1 gun at the stern. Complete dark grey painted as confirmed on 12 February.

Source

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