Caracalla, AE23 of Amaseia, Pontus. 198-217 AD. Dated CY 208 (AD 206/7). 

AY K M AVR ANTWNINOC, radiate head right.
AD CE ANT AMACIA MH NE PR P ET CH, Coiled serpent left on garlanded altar.

Dalaison 418 (D120/R333); 

SNG Copenhagen -; RG -; BMC -. 
Very rare, only one specimen cited by Dalaison.

Another from the same dies sold by Roma Numismatics in Oct. 2008.

CNG Electronic Auction 232, April 2010. Lot 138, sold for $280.
Used with permission of CNG (cngcoins.com), April, 2010