How did Zhouyi divine with copper coins?

If it's copper coins from the Qing Dynasty, that's it. A back note (-) is called Shaoyang. A positive note (-) is called a minor note. The three O's on the back are called Lao Yang, and Lao Yang will become stubborn and gloomy. The three positive notes (x) are called Laoyin, and Laoyin will become Yang.

For example:

change of heart

Six times-

Five times-

Four times o-

Three times-

Secondary-

Once X—

It's that simple.