signsThe square hole厭勝錢

The charm coin — yansheng qian, now more often called huaqian, flower coin — first appears under the Western Han as a variant of the Ban Liang and Wu Zhu cash coins. It was used to speak to the dead, to pray for a good outcome, to frighten ghosts and as lucky money. Over centuries it became a separate commodity with its own shapes and sizes. Unlike a cash coin, which carries two or four characters on a side, a charm often carries more characters, and pictures on the same side.

These were mostly privately funded and cast by wealthy families for their own ceremonies, though governments and religious orders cast some. They circulated alongside official coinage and held value because they were made of copper alloy and Chinese coins were valued by weight in bronze or brass. In periods of copper scarcity they worked as alternative currency — temple coins were issued by Buddhist temples under the Yuan when copper was short or deliberately limited by the Mongol government.

The square hole is not only an opening. It is called an eye, yǎn, and Chinese charms are built on visual puns: a gourd charm made of two Wu Zhu replicas with a bat covering the character where they meet reads as happiness is before your eyes, because bat sounds like happiness and coin sounds like before. A charm's meaning is frequently a rebus you have to hear rather than see.

The forms multiply from there. Open-work charms have irregular openings between the design elements and usually a single large round hole, or a square one where the design is a building. Lock charms are flat, have no moving parts, resemble the character 凹, and were tied around children's necks by Buddhist or Taoist priests; the hundred family lock was funded by a poor family asking a hundred other families each to give a cash coin for a newborn. Pendant charms were worn at the neck or waist from the beginning of the Han, or fixed to rafters, pagodas, temples and lanterns; fish and lock charms were worn mainly by young children and infants. Han pendant charms carry inscriptions like chu xiong qu yang, do away with evil and dispel calamity, and bi bing mo dang, avoid hostilities and ward off sickness.

Qing-era cash coins of the five emperors Shunzhi, Kangxi, Yongzheng, Qianlong and Jiaqing are strung together as a set said to bring wealth and good fortune. Strung coins are also built into swords: in feng shui, coin-swords are hung to frighten demons and evil spirits away.

Chinese charms inspired the same tradition in Japan, Korea and Vietnam, and charms from those countries are regularly mistaken for Chinese ones because the symbolism and inscriptions are close. Chinese cash coins themselves are treated as lucky charms outside China.

A Chinese Numismatic Charms Museum opened on 1 February 2015 in Haikou, Hainan, in a building that replicates the Szechuan Kanting Civilian Commercial Bank in Movie Town Haikou, with about 530 square metres of exhibition space and more than 2,000 charms from the Han to the Republic.