Air Mail cover -- cover addressed to Germany, bearing South America 2m. and 4m. vertical pairs and showing U.S. cachet from the return flight; cover addressed to Sao Paulo, bearing South America 4m. and showing Bahia "drop" c.d.s. on reverse; cover addressed to New York, bearing 8pf. pair and South America 4m. vertical pair; all show the special red cachet, the covers all with some discoloration towards foot