Tenos, Cyclades. AE14, semi-autonomous issue, 1st century AD. 

Head of Poseidon right, trident behind shoulder
THNI, dolphin swimming right.

BMC 39; Paris 468A (this coin); Mionnet IV, 313 corr. (NI overlooked); Dieudonné Inventory 3480 (ditto).

Courtesy of the Bibliotheque Nationale, Paris, gallica.bnf.fr.