Magnet depicts a 1930 U.S. stamp commemorating the first Europe-Pan American round trip flight of the Graf Zeppelin airship in May of that year. The stamps were sold to the general public from April 19 - June 7, 1930 and for an additional 3 weeks to stamp collectors. 1,000,000 of each stamp denomination were issued.
Zeppelins were rigid dirigibles pioneered by a German count, Ferdinand von Zeppelin. The design was so successful that the name Zeppelin came to be applied to all rigid dirigibles. Passenger service was interrupted by WWI while Zeppelins were put to use as bombers and scouts. Passenger and cargo service resumed after the war and flourished in the mid 1930s but Germany's WWII war propaganda and preparation ended the Zeppelin line by 1940.