Chris,
I am particularly interested in the series, searching through my archive of images, through the important Carian
collectionof Erich Karl's sold by
Lanz, and
SNG Finland, i found no symbol similar to yours, however i don't have in hand probably the most important reference
for these, which is the
Jenkins, Rhodian Plinthophoroi, in: Essays Kray- MørkholmI am trying hard to find this reference, any
help is highly appreciated.
It is probably a ''badly" rendered Headdress of
Isis as Pekka suggested (there is a Headdress of
Isis on the example Pekka posted, just under the ''Ο'' on right
field, but it is not mentioned on the description)
however don't hurry to guess that magistrate ΜΑΗΣ is the magistrate of your coin.
Even if we accept the Headdress of
Isis as the symbol of your example, there are coins out there sharing the same symbol
under different magistrate names.
Here for example , is a coin with a Headdress of
Isis to the right, but this time the magistrate is ΕΥΦΑΝΗΣ.
There are probably more magistates under the same symbol, this is very usual on the series, but as i have said before i dont have in hand the major reference to check.
I am afraid we will never be able to identify your piece with absolute certainty. The lack of the magistrate's name is unfortunately crucial.
Best regards