Ivory marked by the Royal African Company. International Slavery Museum, Liverpool. Wikimedia Commons.
Foreign governments asked to trade dollars for American gold, and the vault was the promise.
If money is tight, you never see the gold, but you will live with whatever replaces it.
If you are in the middle, your savings were denominated in a dollar that foreigners were cashing in.
If you have savings, an ounce at $35 was a claim you could see coming apart.
For years foreign central banks had been able to turn dollars in for gold at $35 an ounce.
By the summer of 1971 more of them wanted the metal, and the American stock of it had been shrinking.
The promise was still on the books in early August.
Source: US Treasury gold-window history; Federal Reserve account of foreign claims on US gold ahead of August 1971.