Clyde Friend was bulldozing a driveway around his Yakima, Washington, shop when he first saw them in the dirt: gleaming pieces of the past.

• 克莱．傅连德那时正用推土机在华盛顿州亚基玛市的自家店铺周围整地修筑车道，突然在泥土里发现了它们：闪闪发亮的片片过往陈迹。