There are delis that seem unchanged from the day they opened. Marv’s is one of them. The window is painted with old-time deli lettering; a plastic fern and a fly zapper provide adornment. Unprepossessing? Yes. Disappointing? Never. Herman “the German” Belkin listens to country and western while he pivots between the meat counter, the steamer, and the slicer. “You’re a deli man when your hand is a scale,” he says. His is a loosely formed sandwich, a meat purist’s dream. The tongue and corned beef combination is especially fine, but habitués also come for Belkin’s banter. When it ceases, all that’s heard is the drone of a Miller sign and the caps of Dr. Brown’s bottles, snapped off on the wall-mounted opener, falling to the floor.