Bigatus
In the currency of ancient Rome, the bigatus (plural "bigati") is a type of denarius stamped on the reverse with a "biga", a two-horse chariot. It began to appear in the first decade of the 2nd century BC as an alternative to the "victoriatus", and most numismatists believe that it was not used before 190 BC. A denarius with a four-horse chariot "(quadriga)" had already been in use for some time; see "quadrigatus", likewise named for its chariot icon and depicting in addition the Dioscuri. The first "bigatus" depicted Luna in her two-horse chariot. It continued  in use along with the Dioscuri "quadrigatus" until 170 BC, when the denarius was temporarily suppressed. The denarius was revived around 157 BC with the Dioscuri type and a new "bigatus" depicting Victory in her "biga", probably to commemorate Rome's dominance following the Battle of Pydna. Tacitus and Plutarch mention a statue of Victory in a "biga". The date at which the "bigatus" began to be issued is complicated by the uncertain usage of the word "bigati" by the Augustan historian Livy. In writing about the events of 216 BC, before "bigati" are known to have come into circulation , Livy uses the word to refer to silver money taken as spoils in Cisalpine Gaul or Hispania, and then displayed at triumphs between 197 and 190 BC. "Bigati" may be used loosely for "denarii", and not the specific type. It has also been conjectured that "bigatus" had become a slang term for denarii in a broader sense of "two-horsed," which might also apply to the image of the Dioscuri (Castor and Pollux) as horsemen. None of these explanations has been universally satisfying. In his ethnography "Germania", Tacitus (56–117 AD) notes that while most Germanic peoples in his day still  relied on barter, those along the borders of the Empire engaged in commerce and used currency, but trusted only the value of "old and well-known" coins such as "bigati" and "serrati", the latter being those with serrated edges. Since plated coins had begun to circulate during the time of Julius Caesar and after (see fourrée), they had cause to be wary; however, other older coins should also have relieved them of their concerns, and the reasons for their preference are unclear, especially since plated "bigati" existed.