In several countries with monarchs rulers are often shown on coins wearing crowns.
However Hellenistic monarchs are more likely to be shown wearing a stephanos or wreath or a hat !
Here are some examples:
|Queen Arsinoe 1 wearing a diadem or a modified polos perhaps|
|A Macedonian monarch wearing a headband|
note the headbands or wreaths
finally the one image I found showing something like a crown
however the spikes on this probably represent the rays of the sun
Crowns as we know them developed later