Agathocles of Syracuse
The elephant headdress is seen first on coins depicting Alexander the Great, commemorating his invasion of India, including the (possibly fake) "Porus medallions" issued during his lifetime and the coinage of Ptolemy I of Egypt issued from 319 to 294 BC. It may have had resonances with Pharaonic ideology. The image was later adopted on coinage of Agathocles of Syracuse minted around 304 BC, following his African Expedition. Subsequently it is seen on coinage of King Ibaras of Numidia, a kingdom that Pompey defeated in 1st century BCE, so very likely picked up from there by Pompey's image-makers.