The New York Fed keeps three full sets, plus an electronic version, and it circulates an index. These facts are on the first page of the index, which the lead lawyer for the plaintiffs, David Boies, read aloud in the courtroom last week.

Timothy F. Geithner, who led the New York Fed during the early stages of the financial crisis before becoming Treasury secretary, testified that he kept in his office an abridged version, in a binder about two inches thick, containing the index and a selection of memos. He said he had never seen the full work.

Mr. Geithner in his testimony also played down the importance of the Doomsday Book, saying that he had consulted it infrequently during the crisis because the Fed was quickly forced to take measures beyond anything it had done before.

“We were operating really outside the boundaries of established precedent,” he said.

At times, the Fed may have even decided to throw out the book. The 2006 version contained “an informal opinion by the board’s general counsel that Federal Reserve Banks do not have the power to make non-recourse loans.” Such loans do not allow the Fed to recoup losses beyond the value of the collateral.

Mr. Geithner acknowledged in his testimony that during the recent crisis, notwithstanding, the Fed made non-recourse loans.

But Mr. Geithner, in a memoir published this year, wrote that the Doomsday Book did help the New York Fed deal with the collapse of the investment bank Bear Stearns. The Fed kept the company on life support for a few crucial days by lending money to JPMorgan Chase, which in turn lent money to Bear Stearns.

Mr. Geithner wrote that the idea came from “Tom Baxter, our general counsel, taking a page from the Doomsday Book, the binder full of information about the New York Fed’s emergency powers that he had helped write years earlier.”