Anyone dealt with Electro Copper Plating inside an old mirror? Is it worth breaking the glass to get to the copper plating inside?

There is a lot of weight to the mirror, but I doubt if that's all copper. It might just be a very thin sheet of copper, so it wouldn't be worth the hassle or danger in busting it apart, right? Maybe someone has already travelled down this road and can save me the trouble of learning a hard lesson.

Thanks.