First the archeologists hit bronze, then they found silver.

Israeli archeologists have unearthed a coin in Jerusalem's City of David that, they now believe, was used to pay the head-tax in the Second Temple period, the Antiquities Authority announced.

The rare silver coin was discovered in an archeological excavation outside the walls of the Old City in what was Jerusalem's main drainage channel 2,000 years ago.

Archeologists earlier uncovered thousands of nondescript small bronze coins that were used in every day life, said Prof. Ronny Reich of the University of Haifa.

"A drainage pipe is, not surprisingly, a place where you find lots of history," he said.

In the book of Exodus, Jews over age 20 are commanded to contribute half a shekel each year to pay for public sacrifices and the furnishings of the Temple.

Israeli archeologist Eli Shukron said the coin found at the dig was probably dropped in the drainage ditch by accident.

"Just like today when coins sometimes fall from our pockets and roll into drainage openings at the side of the street, that's how it was some two thousand years ago - a man was on his way to the Temple and the shekel that he intended to use for paying the half shekel head-tax found its way into the drainage channel," Shukron said.

The shekel weighs 13 grams, and shows the head of the chief deity of the city of Tyre on one side, and an eagle upon a ship's prow on the reverse.

Despite the importance of the half-shekel head-tax to the economy of Jerusalem in the Second Temple period, only seven other shekel and half shekel coins have been found in archeological excavations in Jerusalem.