A third century roman coin depicting Alexander with the horns of Amon.
REMEMBER: The imagery of the "horned" king is ONLY, i repeat ONLY associated with Alexander.
Another point: the Quran describes Dhul Qarnayn as reaching the end of the earth and seeing the sun sink into murky waters. There is NO OTHER KING that has the reputation of reaching the ends of the earth. Only Alexander is regarded as a conquerer who reached where the sun sets. (note: there is also a flat-earth error in this Quranic passage).