Numismatic Puzzle: Charlemagne

The piece of today’s puzzle comes from a Künker auction:

France / Carolingians. Charlemagne, 768-814. Denarius, 813/4 or a little later, Aachen. Of the highest rarity and great historical and numismatic importance. Very fine. From auction Künker 394 (2023), lot 4535. Hammer price: 33,000 euros.

Have fun with the puzzle!