Monogramm Karls des Große in Aachen
Charlemagne (c. 742 or 747 – January 28, 814) (or Charles the Great, in Latin Carolus Magnus, giving rise to the adjective form "Carolingian"), was king of the Franks from 771 to 814, nominally King of the Lombards, and Holy Roman Emperor — Imperator and Augustus.
https://commons.wikimedia.org/wiki/Carolus_Magnus
https://de.wikipedia.org/wiki/Karolus-Monogramm