How do the immigrants of Sophora japonica in Hongdong, Shanxi Province prove that they are from Hongdong?

It is said that at the time of immigration, a separated elder bit a child's little toe on his right foot to remind the child of his ancestral home, and the child's toenail became two petals. In the future, whoever has two toenails on his right foot will immigrate from Hongdong. I couldn't see those two petals when I was a child, but I will see them when I grow up.