Due to the small amounts of silver available, the first coins used by the early Republic c. 280 BC were made of bronze. This likely occurred as Roman conquered central Italy where bronze was plentiful. The coins of the period were cast, not struck. Aes Grave were nothing like the Greek coins that had been struck for the previous 350 years. The coinage was based on the libral standard where the As referred to a coin and the weight. One As equaled one Roman pound (or twelve uncia (ounces)). The weight standard changed around 265 BC when the As equaled 10 uncia. This period was known as the light libral standard. The Uncia was 1/12 the value of 1 As. These were issued in large quantities until the introduction of the denarius about 210 BC.