From Bella Online:

One of the more controversial coins of the Ancient World is the Gold Stater of Koson or what is often called the Gold Stater of Brutus. This magnificent coin was struck around 42 B.C., and embodies a story involving murder, war, and suicide. It is no wonder it is a favorite among collectors.

On the Ides of March of 44 B.C., Marcus Junius Brutus, Cassius and a group of Republicans assassinated Julius Caesar. This caused Civil War, and Brutus fled Rome to an area of Greece called Thrace where he raised and army of Dacian mercenaries awaiting the expected backlash of his actions. While in Thrace, Brutus attempted to gain financial backing. It was Polomocratia, the widow of the Thracian dynast Sadalas, who consigned gold to back the army of Brutus.

After Brutus fled Rome, Octavian and Marc Anthony pledged to hunt down Brutus, and bring him to justice in an attempt to restore order and peace within the Roman Empire. They assembled their armies, and began their march.

The Gold Staters of Koson were considered as military payroll for the army of Brutus, and were a part of his ‘War Chest.’ They were minted in the Koson area of Thrace of what is believed to be an anonymous Scythian group. Each of these Greek Staters was made of 8.5 grams of pure gold, and about the size of the U.S. $2 ½ gold piece. The obverse side of the coin is almost a direct copy of the Roman Brutus silver denarii from 54 B.C. It depicts three figures in togas, the middle one being Lucius Junius Brutus, an ancestor of Marcus Junius Brutus, and the other two ligates. Below the three figures is the word “Koson.” The reverse pictures a Roman eagle perched on a scepter while holding a wreath of victory in one of its claws. This is very similar to the type of motif found on many Roman Republic silver and gold coins. Even though these coins look very Roman, and were made to emulate Roman coins, they were made in Greece.

It is believed that all known examples of these coins in existence today originated directly from the ‘War Chest’ of Brutus’ army. A ‘War Chest’ is the payroll from which an army was compensated. Prior to battle the ‘War Chest’ would be buried to prevent its capture by the opposing armies. After the battle, the chest would be dug up and the soldiers would be paid.