The Parthian Drachm
The Parthians where a Hellenistic society that was a growing power in the East in the first century BC. They would become Rome's great rival during the Imperial period. Lucius Cornelius Sulla first encountered the Parthians circa 94 BC - more about this diplomatic encounter in this blog post.
The drachm, a 3-4g silver (AR) coin of parthia and the tetradrachm (4 drachms) are the main coins that I have in my collection. There are also smaller copper coins which are fairly rare.
There is a useful introduction to Parthian Coins here.