Caracalla, barbaric style AE14 of Carrhae, Mesopotamia.interesting coin barbaric imitation. But I have confidence that my coin Caracal. There are signs all the same, but different portraits. What is your Emperor on the coin? http://www.wildwinds.com/coins/ric/caracalla/_carrhae_BMC_015_2.jpg Elagabalus, AE16 of Carrhae, Mesopotamia. AYT ANTWNEINOC, radiate head right / KAR KOL M P, crescent and one star on globe and serpents. Mionnet V, 31a. http://www.wildwinds.com/coins/ric/elagabalus/_carrhae_Mionnet_V_31a.jpg
I don't think yours is barbarous. Very nice example though. Mesopotamia, Carrhae. Elagabalus AE17 Obv: Radiate bust right. Rev: KAΡAKOMH, Crescent with star, pendant fillets and pellet below. 17mm and 2.8g.
Whether it's Elagabalus or Caracalla seems to be the question and since I don't have any barbarous examples at all I'll guess it's Caracalla as you seem to think---but I wonder if it is a barbarous example or simply 'Provincial'.
It seems to me that this is the style of barbaric, but the previous author - Aniecintone probably knows better than me, and I believe him. Most likely it Elagabalus and a regular circulation of this coin…….
here is a similar coin: ROMAN PROVINCIAL MESOPOTAMIA CARRHAE Elagabal AD 218-222 Bronze. 15 mm. 2,14 g. Obv: Radiate, draped and cuirassed bust left, seen from behind. Rev: KAP KOΛ MHTPΟΠΟΛ; Star within crescent. BMC 15cf var (right). gVF Rare https://www.ebay.de/itm/LANZ-MESOPO...5BVz1WPfxQ%3D&orig_cvip=true&nordt=true&rt=nc
BMC specifically mentions that the difference between Caracalla and Elagabalus from Mesopotamia are often impossible to determine and that either attribution could be correct.
Many years ago I collected the coins of Carrhae and had acquired some 70 coins. I came to the conclusion that the small ae coins with the KO(L) MH KAP reverse legend were minted during the reign of Elagabalus. I came to this conclusion because many featured obverse portraits wearing a radiate crown but were not bearded. Stylistically the small laureate aes as well as the radiate aes seem to form a homogeneous group. I do not have these coins anymore. Around 2003 I visited a friend who collected Mesopotamian coins and we did a lot of trading.
Here is another, apparently, a silver coin of Mesopotamian from the same old collection of coins 6 or 7, which I bought.