United States: Postal History 1930, Graf Zeppelin Europe-Pan American Flight group

United States: Postal History
1930, Graf Zeppelin Europe-Pan American Flight group,
of two covers and one card, each franked with one of 65c, $1.30, and $2.60 Graf Zeppelin, postmarked between 29 April and 30 May, each with dual USA and German flight cachet, the $1.30 example on cover to Sweden, chiefly fine-very fine, a desirable group of this popular set of Zeppelin Air Posts. (Sc. C13-15)
Cover