The bird is not a Thunderbird, it looks more like what is called a Peyote Bird, aka the Water Bird. However, the historical origin of the Peyote bird is not from any of the southwestern tribes, but originated with the tribes of the mid-western plains. I am not a jewelry expert, with the exception my wife and I got to Santa Fe every year for our anniversary and I buy her something every year! And let me tell you, I've seen this image a lot in modern southwestern design. Not sure how far back that tradition goes. Any markings on the inside?