sentences:  While in ancient Korea various items like clam shells, iron, and precious metals were all traded as a medium of exchange, but the primary forms of currency during this era used in bartering were grain and cloth.During the pre-monetary times anything related to food and clothing was used as a medium of exchange as well as a method to measure the value of products.The types of grains most commonly used for bartering were rice, barley, beans, and millet.