airmail cover franked with 10c Orange, 20c Red violet, and 40c Yellow (C9, C11, C13) tied by October 18, 1933 Cristobal machine cancel, endorsed "Graf Zeppelin From Miami to Chicago" and postmarked Miami October 23, October 24 Chicago general delivery backstamp, very fine and scarce cover with Canal Zone stamps paying the 50c postage from Miami to Chicago via Graf Zeppelin