I received a reply on another inquiry I had sent to a gemologist to see if he could identify the stone on the ring, but he was unable to provide a conclusive identification since the stone isn't polished and the photo does not provide enough detail. He did indicate that it may be Jade or nephrite, a type of Jade. His suggestion was to have the stone examine in person by a qualified gemologist.
I'm beginning to think that perhaps the ring originated in China? Perhaps the markings on the inside of the band are faded Chinese characters?