File talk:Quaterionenadler David de Negker.jpg

The coat of arms referred as "Maidburg-Hardegg" in fact refers to the burgraves of Magdeburg, from the Querfurt family. You may see their coat of arms, same as in the eagle, here http://wappenwiki.org/index.php/House_of_Querfurt and here https://de.wikipedia.org/wiki/Querfurt_(Adelsgeschlecht)