"In ancient in the earliest times barley was the medium of exchange for most transactions. ...grain continued throughout these centuries to be the standard of payment and repayment. However, even before 3000 B.C., ingots of copper and silver were also exchanged. There were two standards of value: grain and silver. Silver was used mainly in the town economies... while grain was used in the country. There was no coined money until the first millenium B.C.; payments in metal were by weight."