To find the value of an old coin -- other than having it appraised by a coin expert -- one should examine it based on a number of factors. Some factors that affect coin value are age, rarity, condition, design and country of origin.
To determine a coin's age, one should look for deviations from normal dating methods. The date on the coin may differ from the minting date, or it may be derived from a different calendar system, such as the Islamic system. Also, one should determine the coin's country of origin because the country's history and minting practices may affect the quality and demand for the coin.