What does Schindler value Stern so highly?

Itzhak Stern is Oskar Schindler's accountant. He begins working with Schindler as Jews are being moved to the ghetto. An intelligent man, he is the first to realize that Schindler's facotry can be used as a safe haven for Jews. He forges papers for Jews and employs them at Schindler's factory. He is the man who appeals to Schindler's moral side and by the end of the film, the two men have grown affectionate for one another.