Pure silver, also referred to as fine silver, has actual silver content of 99.9%. Because of its high purity, fine silver is too soft to use in jewelry making and is often mixed with other metals to make it harder.
Usually, sterling silver has a purity of 92.5%, meaning that 7.5% of the alloy is made of copper or another metal (usually nickel or zinc).
Fine silver is stamped with marks such as 999, 99.9 or .999, indicating how much silver the piece contains per hundred or thousand parts.

It is widely believed that it will ward off evil spirits and calamities.

A "Long-life lock" 长命锁 expresses a person's best wishes for the child's good health, good luck, opening the "lock" of a child's wisdom too.