I would like to thank MacroLuv/Nikola for (unintentionally) giving me the idea of doing a project on this coin. I bought this coin over 30 years ago and only today with help from another forum (Yahoo Moneta-L) have I been able to confidently attribute it to the licenced monier.
It is a silver denarius from the time of the Roman Republic, coined (in Rome) under the authority of monetary magistrate Lucius Antestius Gragulus in 136 BC. Diameter is 19mm at longest point.
The obverse carries the winged (helmeted) head of Minerva (or Palas) in the personification of Rome. Although difficult to read, behind the head are the letters GRAG (for Gragulus). The reverse shows the god Jupiter holding a sceptre in his left hand and a thunderbolt in his right. Hi is driving a quadriga (4 horse chariot). Below the chariot is the monogram of Lucius Antestius (looks like L.AE..).
Although clearly struck from a different pair of dies, this is what a near perfect coin should look like :
http://www.wildwinds.com:80/coins/sear5/s0115.html
And here is my coin (Meiji EMZ-5TR and Olympus SP-350):


Bruce