C18 on cover to Germany - Delivered via the "Graf Zeppelin" - Exposition cachet

The #C18 (50¢ Green "Baby Zepp") was the specific stamp issued for the Graf Zeppelin's flight to the 1933 Chicago World's Fair.Only 324,070 of the official C18 stamps were sold, with a significant portion used on flown covers.

Covers that completed the full international journey from Akron to Friedrichshafen, Germany are highly sought by collectors.