1999 $1 Silver Kangaroo Frosted Uncirculated Coin. The kangaroo family, known as a Mob, usually mix together in large groups when there is plenty to eat. The biggest male in a mob, called a Boomer, can stand as tall as a man and propel himself forward thirty-three feet in one single jump. Once the food supply is exhausted, mobs travel together in search of fresh grass and water. During this time a joey will stay in its mother's pouch for around 230 days, where it is safe and warm. From time to time it will venture out, only to return when frightened. This coin features a kangaroo family. Please contact Adelaide Exchange Jewellers to find out more on this item.