I have to admit that I am a little uneasy about the gold stater.
On the obverse, there seems to be a join line on the circumferece from 9 o'clock to 12 o'clock, and
on the reverse, on the circumference, from 12 o'clock to 5 'clock.
I really would love for that uneasiness to be settled and for me to be proven wrong.
The weight is 'spot on' for this coin, and it appears to be made of good gold, and the style looks very genuine.
Perhaps you could take it to a professional dealer in ancient coins who has a well established reputation in his field.
Is it possible that you could find more about this coin from the guy who formed the collection out of which it originally came?