This is German rocket mail with a postmark for Westernoche (WW) 30.7.61 (July 30, 1961).  This was carried aloft on July 29th at Westernohe by rockets launched as indicated by the special rocket cachet in black ink to the left.  Rakete Folke Bernadotte was named for Count Folke Bernadotte, former member of the Boy Scouts International Bureau who was killed in Palestine.  Only 250 covers were posted with the Folke Bernadotte cachet below.

A 1DM rocket seal is printed in tan and green on the envelope.  The stamp providing surface postage was issued on April 22, 1961 honoring Scouting's 50th Anniversary.  The stamp depicts St. George, patron Saint of Scouting.

A second rocket - "Rakete Guy de Laurigaude" was flown with 250 covers.  An unknown number of covers marked for the test flight were carried aloft.  There is also a First Day Cover for the event that was not flown.

SOSSI Journal Volume 10, Number 10, October 1961
Ellington-Zwisler Rocket Mail Catalog,
American Air Mail Society, 1967
Dr. Max Kronstein, Rocket Mail Flights of the World to 1986
The American Airmail Society, Cinnaminson, NJ 1986.