Ptolemaic Egyptian coins were usually of silver, their weight based on a silver standard. On the obverse is the profile of Ptolemy I. A chunk of silver was cut out of the king's cheek in order to test the coin's content and prove that it was pure silver. On the reverse is an eagle clutching a thunderbolt, both symbols of Zeus. The Ptolemaic kings claimed legitimacy via closeness with Alexander the Great, who believed he was the son of Zeus. A mint mark in front of the eagle indicates that this coin was minted in Cyprus, which at the time belonged to Egypt.