Obviously since it is a matrix allowing then to shape “positives”....
I don't have the backs, they are two different sides.
I called them "Chinese"...Could they originate from French Conchinchina or from another colonial trading post?
In the 19th century it was customary to make molds of tortured rebels
after their execution this for dissuasive purposes (pedagogy of the time).
It is probably this type of object.
Impossible to ship them, hand delivery should be considered. or by carrier