This is a non portable “Gold gab Ich Für Eisen” medal, or as is written officially on the reverse side of the medal: “Gold gab ich zur Wehr, Eisen nahm ich zur Ehr” (gold i donated for defense, iron i took for honor).
These were given to people who donated their gold items for the war effort of World War I in Germany. As the war was very expensive the German government (the army!) needed more money to finance the war. People were thus called to donate their jewelry and gold items. In return they got the medallion.
The medaillions were shown with pride, as it meant the owner donated for the war.