Series for Airmail (complete series 9 values with eagle like "537" in different colors plus one each of Lilienthal and Zeppelin)
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>