I am definitely not an expert, but previously toured some ancient rich Chinese houses, some actually paint a picture of a bat at the main door.
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Extracts from a website on coin bearing bats.
http://primaltrek.com/gourd.html
Surrounding the character fu (福) are five flying bats. A bat (fu 蝠) is a visual pun for "good fortune" or happiness (fu 福) because both characters are pronounced the same.
The bats at the top are shown flying upside down. In Chinese, the character (dao 倒) for "upside-down" and the character (dao 到) meaning "to have arrived" are pronounced the same. If you say "the bat is flying upside down" a listener could just as easily interpret this as "happiness has arrived".
The depiction of "five bats" is a traditional representation of what is known as the "Five Blessings", also known as the "Five Happinesses" or "Five Good Fortunes". These five blessings refer to longevity (寿), wealth (富), health and composure (康宁), virtue (修好德), and the desire to die a natural death in old age (考终命).
The wish for good fortune is further reflected in the Chinese four character inscription located at the three o'clock and nine o'clock position. The inscription reads wu fu lin men (五福临门) which means "may the five fortunes arrive at your door".