It may be an indian nation plate. Most indian tribes/reservations are allowed to issue their own license plates to members. It should say on the plate what nation where the state name would be. For ex: Choctaw, Potowatamie, Sac-Fox, etc. Bird and star variations are common i think. One of the tribes in our area has something similar. The eagle is a sacred bird to many tribes so that would make sense. A five point star could stand for a five tribe confederation like the Iroquois or the five civilised tribes or something. Thats just a guess tho.