I recently acquired a FM copper Mech mod by Blacksmith with a Stillare rda on top. The setup was given to me by a friend which had been gifted to her, so I have no way of knowing the authenticity of either. Is there a good way to differentiate the FM from its clone or will it remain a mystery? It's also not new, which makes it more difficult to see details, such as the signature at the bottom (which is present)