Just before Christmas, 1940, Nazi aircraft flying over the United Kingdom from Norway bombed the harbor at Oban, Scotland, sinking a loaded cargo ship bound for Bombay, the S.S. Breda.–For five decades the wreck sat beneath the dark waters, her location well known to divers. But her strongroom remained sealed shut, its contents a mystery. Was there gold in that undersea vault? Jewels? When it was finally opened, divers were disappointed to instead find piles of blank sheets of white paper. Upon further inspection, they realized they’d salvaged something even more rare than precious metals: a cache of watermarked banknote sheets en route to the Reserve Bank of India. The so-called ”treasure sheets“ comprise what some experts consider the most numismatically unique shipwreck find of all time.