It’s the biggest mystery on Wall Street. Hurricane Sandy floodwaters inundated a 10,000-square-foot underground vault downtown, soaking 1.3 million bond and stock certificates — including bearer bonds that function like cash — and putting them in danger of turning to mush. A contractor working for the vault owner, the Depository Trust and Clearing Corp., is feverishly working to restore the paper. But the value of the threatened notes under 55 Water St. remains unknown to all but the innermost circle of Wall Street bankers. One source said $70 billion in bearer bonds were in jeopardy. (full story)