31 U.S.C. § 5133

1. (a)The Secretary of the Treasury shall—
   1. (1)charge the superintendent of each mint with the amount in weight of standard metal of bullion the superintendent receives from the Secretary;
   2. (2)credit each superintendent with the amount in weight of coins, clippings, and other bullion the superintendent returns to the Secretary; and
   3. (3)charge separately to each superintendent, who shall account for, copper to be used in the alloy of gold and silver bullion.
2. (b)
   1. (1)At least once each year, the Secretary of the Treasury shall settle the accounts of the superintendents of the mints.
   2. (2)At any settlement under this subsection, the superintendent shall—
      1. (A)return to the Secretary any coin, clipping, or other bullion in the possession of the superintendent; and
      2. (B)present the Secretary with a statement of bullion received and returned since the last settlement (including any bullion returned for settlement).
   3. (3)The Secretary shall—
      1. (A)audit the accounts of each superintendent; and
      2. (B)allow each superintendent the waste of precious metals that the Secretary determines is necessary—
         1. (i)for refining and minting (within the limitations which the Secretary shall prescribe); and
         2. (ii)for casting fine gold and silver bars (within the limit prescribed for refining), except that any waste allowance under this clause may not apply to deposit operations.
3. (c)After settlement, the Secretary shall compare the amount of gold and silver bullion and coins on hand with the total liabilities of the mints. The Secretary also shall make a statement of the ordinary expense account.
4. (d)The Secretary shall procure for each mint a series of standard weights corresponding to the standard troy pound of the National Institute of Standards and Technology of the Department of Commerce. The series shall include a one pound weight and multiples and subdivisions of one pound from .01 grain to 25 pounds. At least once a year, the Secretary shall test the weights normally used in transactions at the mints against the standard weights.