The Coin of Solomon is one of the 13 artifacts. The Coin gives the bearer epiphanic leaps of knowledge and jumps in evolutionary biology.
After a bank robber found the Coin of Solomon, he brought it to a broker for evaluation. The broker found it extremely valuable and killed the robber and took the coin for himself. While walking on the streets, he dropped the coin, a friendly homeless guy found it and gave it back to the broker. Later the broker was hit by a car and died, and the coin rolled down the street in an impossible path and found it's way back at the homeless guy, who seems to be picked by the coin to be it's wielder.
The Coin of Solomon was found on one of the crime scenes by Sara Pezzini and Jake McCarthy. Jake picked it up and it merged with his forearm. Pezzini's Witchblade reacted quickly and forced the Coin out of Jake's body. A random bystander then found it in the hallway where it landed and took it for his own. The bystander never returned to his home that night; his fate is unknown.
The Coin of Solomon, however, was eventually found within the chest of Aphrodite IV, during the the plot of bringing the 13 Artifacts together by the Curator.
In the future, Aphrodite IX also has the coin, imbedded in her frontal lobe, put there by the Chairwoman.