I am searching for information about a specific theorem mentioned in the book "Discriminator-algebras: algebraic representation and model theoretic properties" by Heinrich Werner. The theorem in question is said to provide a way to construct a mathematical structure from a set of functions that satisfy certain conditions and closures, and this structure has precisely those functions as the set of all isomorphisms between all its substructures. I think the theorem is attributed to Stone in the book.

Thank you very much for your attention and assistance!