Roman coins include the aes rude, the as, the aes grave, the denarius and the aureus. The term aes rude was the earliest used to describe the very first pieces of bronze that were exchanged instead of cattle as a form of currency.
The term aes rude was changed at the start of the third century BC, when markings were added to the bronze. The marked bronze coins were called "as." The "as" was divided into smaller units by weight. These units were called aes grave, but there were even smaller denominations produced.
In 187 BC, the entire currency system was changed and with it, the denarius was introduced. This coin was silver and had the value of about 10 of the "as" coins. The aureus was introduced later as a gold coin, and was in circulation along with the as and the denarius.