U.S. National Archives (Record Group 104, [Denver] Entry 22, Letters Sent to the Director of the Mint) Public Deposited
National Archives (NARA) catalog description: This series consists of copies of letters sent to the Director of the Bureau of the Mint from the Superintendent of the U.S. Mint, Denver. The letters in this series concern general administration, including accounts, fiscal matters, personnel issues, equipment, and supplies. Some of the correspondence relates to shipments of bullion, assaying work done for the Forest Service and the General Land Office, and reports on the value of gold and silver. Also included in this series are copies of letters sent by the Superintendent to other officials, primarily the Melter, Refiner, and Assistant Secretary of the Treasury.
Link to National Archives catalog record: https://catalog.archives.gov/id/2657775. See also the National Archives & Records Administration numismatic finding aids at https://nnp.wustl.edu/library/archivedetail/538870.
Note, the entry number (22) is reused at Denver. In the Philadelphia NARA series, entry 22 refers to correspondence related to the sale of cent planchets. The Denver entry is physically organized as 16 volumes in 5 boxes, covering the period July 15, 1929 to August 20, 1934.