The Key in the Satin Pocket (Nancy Drew Series #152)

When Nancy tries on an old brocade jacket in a vintage clothing store with Bess and George, she finds an old safe-deposit box receipt in the pocket and a key sewn into the lining. Soon the girls are tracing items from an old estate scattered in antiques shops across town—and are immersed in a mystery involving long-lost relatives, a missing will, and a hidden fortune.