The eagle is taken from the "Wappen" of the Mark Brandenburg, seat of the Hohenzollern kings of Prussia. Much the same eagle became the "Reichsadler" of the Second Empire in 1870. Bismark and the boys.
BMW RA chose this symbol because BMW motorcycles are made in Berlin, not Munich, and Berlin is in the Mark Brandenburg, in Prussia.
Thereto appertaining, we have a number of large, beautiful Imperial Navy flags with eagle and iron cross which we had planned to fly at rallies. Unfortunately, a wacko skinhead party in Germany had the same idea, so we restrict ourselves to using the eagle only--until the neo-fascist morons go away and are forgotten.
The eagle (and the Iron Cross) have far more ancient associations than with the first World War. And the eagle has none whatever with WW II. It should be noted that the German air force still has the Iron Cross on its planes.
For a long time our front page eagle faced the wrong way, so we recently changed it. No one noticed.