Series for Airmail, 100 day of birth of Ferdinand von Zeppelin (1838–1917)
scanned by <a href="//commons.wikimedia.org/wiki/User:NobbiP" title="User:NobbiP">NobbiP</a>
scanned by <a href="//commons.wikimedia.org/wiki/User:NobbiP" title="User:NobbiP">NobbiP</a>