This is a celtic gold stater from Ambiani
Ref : Scheers série 24, classe II, LT 8710, Seaby (greek coins) 121var.
AV 6g16
Obverse : uniface
Reverse : Stylised horse right .
From ELSEN 56, n°36 (December 1998) : 14 000 Fb (about 350 euro)