Now I asked exactly that question of my co-writer of the 'Three Sisters', and here is his answer:
Its name is the Death Signage(亡命牌), and it is a uniquely Chinese marking of a condemned prisoner. It is a wooden mark with the prisoner's name and crime written on the back of the condemned prisoner, and a way to humiliate the prisoner, very common in Chinese justice and a sign of execution in China. At the time of execution, the sign is removed, signaling that the prisoner's life has disappeared from our real world.
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The red X's I don't know.