The Heaven and Earth Society, as an underground association, is a secret organization advocating the overthrow of the Qing Dynasty and restoration of the Ming Dynasty.
Within the organization, there is a concept known as "Hong Money", primarily used for mutual identification.
"Five sets of long coins twenty-one, stay at the bridgehead to buy fruit. Gather inside Mud City, thousands come to share one bond."
This verse is the secret code of contact for the Heaven and Earth Society, indicating membership through twenty-one coins (according to the Society's secret language, the number three eight twenty-one implies the word "Hong").
According to old records passed down from the Heaven and Earth Society, there were three types of Tongbao before the Pangu Tongbao within the Society, used as proof of membership.
However, these three types of Tongbao only have suspected photographs and have never been confirmed by any real object.
