Old Metal Powderhorn-Dug up

My nephew was washing off his yardrake across the road from his house when he saw something shining underneath an oak tree. After carefully digging underneath a root he realized that it was the tip end of this powderhorn. Three days later he searched again and found the latch that had broken off because of hair like roots that had entwined around it over the years of being underground. He had it acid tested and was told it is silver and a lady that buys gold and silver told me that it is silver and very old. My nephew has lived at his place for 38 years and our family has lived here for over 100 years and this is the first time it has been seen. We would be so thankful if someone could tell us something. It has a family crest and double eagles mounted on it.