This meant that for every ounce of silver in the U.S. Treasury's vaults, the U.S. government could continue to issue money against it. However, stamp overprints which were used under the "Silver Purchase Act of 1934" to finance the nationalization of U.S. silver mines, and also carried taxes ranging from 1¢ to $1,000, ended in 1943. These silver certificates were shredded upon redemption since the redeemed silver was no longer in the Treasury. With the world market price of silver having been in excess of $1.29 per troy ounce since 1960, silver began to flow out of the Treasury at an increasing rate. To slow the drain, President Kennedy ordered a halt to issuing $5 and $10 silver certificates in 1962. That left the $1 silver certificate as the only denomination being issued.