William Bolden examining lists of 20 dollar bills. "I am proud to be involved in the creation of what is widely used around the world," he said..

William Bolden, left, and his colleague, Avery Delhert study lists the 20-dollar bills.

Banknotes are packaged in packs of two thousand dollars..

Denominations strong enough to bend and unbend them 4,000 times, only then they can break.

Lydia Washington, a representative of the U.S. Bureau of Engraving and securities in the U.S. Treasury, says that only the Office 1368 employees, and they produce per day can be cuts in the total cost of 974 million dollars. "We have set world standards in the production of currency," she said. "Our currency is very high quality and is not depreciated.".