There could be some slight pitting of the patina, but it would be very light. The legend on the coin should be pretty sharp and readable. AE- means this is a bronze coin. AR- means this is a silver coin. AV- means that this is a gold coin.
Bronze is an alloy of copper.
It can appear to be anything from reddish copper to yellowish brass. This may sound easy, but roman silver often had a lot of lead in the coinage. On the other hand Greek coinage tends to be much purer. While the values are in pounds, this is still the best book for attributing roman coins. David Sear has also written books on Greek and Byzantine coins.