Chinese coins are a potent symbol of wealth and prosperity.
The coin is one of the "Eight Treasures".
Ancient Chinese coins are round with a square hole in the middle which reflects the Chinese view of the earth as square and the heavens... as a circle.
A coin (qian ?) can be a visual pun for "before your eyes" because the hole in the center is called an "eye" and the coin (qian) has the same pronunciation as the word "before" (qian ?).
An old word for coin is quan (?). A pair of coins is shuang quan (??) which has the same pronunciation as "both complete" (shuang quan ??).
See a charm incorporating a "pair of coins" as a visual pun or rebus at Bagua Charms.
For a history, including images, of ancient Chinese coins and other forms of money please visit Chinese Coins.
Yin Yang (??) is the Chinese term for the basic polarities of the universe, e.g. male/female, light/dark, strong/weak, etc.
The "supreme ultimate" symbol, known as taiji (??), is a circle with an S-shaped curve separating it ...into two equal halves. One half represents yin and the other half represents yang. In the center of each half is a small circle which represents the other half.
A representative charm with the taiji symbol can be seen at the Book of Changes and Bagua.