The U.S. Mint Public Enterprise Fund
"Pursuant to Public Law 104-52, the Public Enterprise Fund (PEF) was established to account for all revenues and expenses related to production and sale of numismatic products and circulating coinage and protection activities. Expenses accounted for in this fund include the cost of metals used in circulating coin production, the cost of non-Treasury metals (platinum, cupro-nickel, and zinc) used in numismatic coin production, fabrication and transportation-in costs for metals used in circulating coinage and numismatic products, and costs of transporting circulating coinage between Mint production facilities and Federal Reserve banks. Other costs/expenses accounted for in this fund include costs related to research and development and purchases of equipment, as well as capital improvements. P.L. 104-52 states that any amount in the PEF that is determined to be in excess of the amount required by the PEF shall be transferred to the Treasury."
-United States Mint 1999 Annual Report, Notes to the Financial Statements for Fiscal Year Ended September 30, 1999