פירוש על עבודה זרה 81:4

Like a ball - That the world is round, as stated in the Jerusalem Talmud, that Alexander of Macedon ascended above until he saw all of the world like a ball, and the sea like a basin, meaning the great ocean that entirely encompasses the Earth.

The staff, bird and orb are symbols of power. If the image holds one of them, it is certainly a royal idol of sorts.