Diamond-jewelry retailer Signet Jewelers, which owns Zales and also operates Kay Jewelers and Jared brands across the country, is overvalued, according to a hedge fund manager. The company sold its books of credit to outside vendors this year, which will cut into critical holiday sales, said Matthew Kliber, who runs a short-selling hedge fund at Gracian Capital. Kliber made the remarks on Monday at the Kase Learning Shorting Conference in New York.