A treasure, possibly worth half a million dollars, may lie behind a granite slab at the base of the Bloomingdale’s flagship store in Manhattan, just a few feet from a window displaying designer handbags: a baseball signed by Babe Ruth.

On April 23, 1930, according to several newspaper accounts, the ball and some other valuable items were entombed in a cornerstone there, at the northeast corner of Lexington Avenue and 59th Street, marking the beginnings of an addition to the store.

“Hundreds of shoppers halted at the scene,” The New York American reported the next day, as the polished granite was lowered by rope while store executives and city officials watched from a platform, top hats in hand and boutonnieres in the lapels of their suits.

The stone looked about the same last week, its “Erected 1930” engraving nearly as sharp as it was in pictures from 87 years ago. A young man, wearing a black leather jacket and chomping on gum, leaned against the engraving and fiddled with his cellphone.