What was the significance of bronze mirrors in ancient Japan? -

I m researching some things on ancient Japan, and while reading, I ve come across quot;bronze mirrorsquot; a few times. I ve tried finding websites to help me, but I just can t find an answer to my question. All I want to know is why they were so important, and perhaps some stories with them. If you know anything, please answer. Thank You!

It was said that in Japanese myth, if one could see themselves in a rusted (with the green stuff) bronze plate, they could be declared equipped with beauty beyond compare and honorability.