A federal judge ruled Thursday that Native American plaintiffs are entitled to $455 million in a long-running trust case, a fraction of the $47 billion they wanted.

But U.S. District Judge James Robertson did not say how the government should award the money, writing that his opinion "leaves for another day the question of how and to whom the award should be distributed."

Robertson's final number is close to government estimates and far from the billions sought by plaintiffs in the 12-year trial. The lawsuit - filed on behalf of a half-million Native Americans and their heirs - claims they were swindled out of billions of dollars in oil, gas, grazing, timber and other royalties overseen by the Interior Department since 1887.

The judge said he will have to hold another proceeding to decide how the money will be awarded, hinting that he hopes for a settlement between the two parties before then.

"Perhaps it is not too much to hope that the announcement in this memorandum of a hard number will give rise to some off-line conversation between the parties in the meantime," Robertson wrote.

At issue was how much of the royalty money was withheld from the Indian plaintiffs over the years, and whether it was held in the U.S. treasury at a benefit to the government.

Robertson said in the opinion that plaintiffs did not successfully argue that the money was of benefit to the government over the years, significantly reducing his final estimate of what the Native Americans were owed.

Because many of the records have been lost or destroyed, it has been up to the court to decide how to best estimate how much the individual Native Americans- many of whom are nearing the end of their lives - should be paid.

During the course of the trial, plaintiffs reduced the amount they said they were owed based on documents that became available in the proceedings. They settled on $47 billion, down from their estimate going into the trial, which was $58 billion. Earlier estimates were as high as $100 billion.

Filed by Blackfeet Indian Elouise Cobell, the lawsuit deals with individual Native American's lands. Several tribes have sued separately, claiming mismanagement of their lands.