French steamship St. Firmin visited the Black Sea according to a letter of the German naval attaché at Istanbul dated 22 December 1939

In his letter dated Istanbul, 22 December 1939 No. 575g reported the German naval attaché to the Oberkommando der Wehrmacht Abteilung Ausland the steamships passing Istanbul. An item reported that the French steamship St. Firmin unloaded not 12 but 16-24cm Skoda guns.

Source

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