What is the ruling on using copper for headaches, joint pains, and repelling the evil eye?

If the efficacy of copper treatment is proven by experience or by the report of a trustworthy physician, then there is no legal impediment to its use, just like any other form of treatment. However, wearing it merely out of a belief that it brings benefit or repels harm is forbidden and falls under the ruling of hanging amulets, and its practitioner is oscillating between major and minor Shirk (definition) (polytheism).