In accordance with the United States Mint regulations, a charge of four cents per $100 is made for what are known as commercial bars of gold, which are from 990 to 997 thousandths fine. The shipper has to pay for these bars with gold coin, which is obtainable without charge at the Subtreasury in exchange for gold certificates or for legal-tender notes. There is no restriction upon the withdrawals of gold from the Subtreasury for export, and the shipper has the option of taking coined pieces, if he prefers, but the loss by abrasion of coined pieces practically equals the cost of 4 cents per $100 charged by the mint for commercial bars, which are put up in that shape to induce exporters to take bars instead of coined pieces, and thus save the government the cost of coinage as well as the transportation of the bullion to the mint.