The BMW VI-engined Dornier Delphin III (Do L Bas) flying boat D-UBIF, Konstanz, Werknummer 152. The boarding pier for crew and passengers can be seen behind the fuselage. This aircraft was built at Dornier's facilities in Altenrhein, on the Swiss side of Lake Constance, and at one point in its existence also displayed the Swiss registration CH-178.
According to the inscriptions on the back of these photos, they were taken at the Lake Constance shore promenade in Konstanz, Germany, in 1935 or 1936. (Fischer collection)