Are the diamonds old mine cuts? The cut of the stone will give you some idea of the age of the ring.
Northwest Georgia was the sight of some really horrendous battles in the civil war. Anyone that had anything of value was either burying it, hiding it or running with it. And it was not easy to run with a lot of coin, the family silver and the good china.
Sherman's army went through Georgia looting, burning and raping until they reached the sea.
You definately need to work the property with a metal detector.
Rufus
P. S. Keep your mouth shut about anything you find. You know how governments like to glom onto anything of value.