Original 1935 U.S. airmail/balloon “stratosphere flight” souvenir cover from the Black Hills series, sponsored by the U.S. Army and the National Geographic Society. Front features the magenta cachet reading “Third Black Hills Stratosphere Flight – U.S. Army & National Geographic Society” with balloon/stratosphere artwork.

Postmarked Rapid City, South Dakota, NOV 11, 1935 (5 AM) and addressed to J. C. Valentin, Chicago, Ill. Franked with a 3¢ California Pacific International Exposition postage stamp, tied by machine cancel.

These Black Hills Stratosphere Flight covers relate to the 1935 high-altitude balloon program connected to National Geographic/U.S. Army stratospheric research, making them desirable crossover material for airmail, balloon mail, and aviation/space-precursor collectors.

Condition notes:

• Used/postally carried cover.

• Light age toning and handling wear.

• Corners/edges show mild wear; a couple faint wrinkles/creases from use.

• Cachet remains bold and legible.

• Stamp present and securely tied by cancel.

• Back is clean overall with light pencil notations from a prior holder.

Item details:

• Type: Postal cover / airmail souvenir flight cover

• Event: Third Black Hills Stratosphere Flight

• Cancel: Rapid City, South Dakota, Nov 11, 1935 (5 AM)

• Cachet color: Magenta/pink

• Stamp: 3¢ U.S. commemorative (California Pacific International Exposition issue)