The nearly completed first Dornier Do X, D-1929, photographed at Dornier's facilities at Lake Constance, in Altenrhein, Switzerland, approximately June 1929.
One of the Siemens Jupiter engines is fitted with a Bremspropeller [drag propeller] for engine test runs. Lower detail photo shows nautical horn cleat mounted to forward fuselage, used to secure the ropes that tie the flying boat to its moorings. (Fischer collection)