Caracalla, AE23 of Plotinopolis, Thrace. 

AUT K M AUR ANTWNEIN, radiate, draped, cuirassed bust right.
PLWTEINOPOLEITWN, The three Graces standing facing. 

Varbanov 1863 (this coin).

Courtesy of Mark Staal, author of "The Three Graces and their
Numismatic Mythology", April 2011.