My Thoughts, although I can't find any historical proof, is that the gold that is/was owned by the U.S. is being held as collateral by the twelve original shareholders in the FED, until such time as the U.S. repays its debt(s) to them.

One of the reasons that the U.S. continues to value its gold at such a low rate ($42-$43), imo.

(Remember ESL bringing up an entry on the U.S. balance sheet, that indicated the potential sale of the U.S. gold, but didn't think much of it at the time. Will try to find and analyse.)

Good Luck to all!