PORTRÄTPOSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst Dating: 14.11.1906
BILDPOSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Haeckel, Ernst; Haeckel, Agnes [Eltern] Dating: 10.04.1909
BILDPOSTKARTE Haeckel, Walther Author: Haeckel, Walther Recipient: Schmidt, Ernst [incognito Ernst Haeckel] Dating: 30.03.1907