Sept 1929: This is Catapult mail from New York (the sender's address is faintly visible on the back) to Vienna; the aeroplane was catapulted from the 'Bremen' as it approached Cherbourg, and landed at Munich. [All these flights are extensively documented, down to the names of the crew.] WIEN 101 is Westbahnhof - perhaps it came from Munich by overnight train - and WIEN 28 is Nordbahnhof where it arrived at 8:40 am. Schwaigergasse, the delivery address, is across the Danube in Floridsdorf.