"This exhibition is the first to examine an intriguing but largely unknown side--in the literal sense--of Renaissance painting: multisided portraits in which the sitter's likeness was concealed by a hinged or sliding cover, within a box, or by a dual-faced format. The covers and reverses of these small, private portraits were adorned with puzzlelike emblems, epigrams, allegories, and mythologies that celebrated the sitter's character, and they represent...