U.S. National Archives (Record Group 104 [Denver], Entry 2, Assayers' Registers of Gold Bullion, 1863-1916)
National Archives catalog description: This series consists of assayers' registers of gold bullion. These registers list the date of the assay, the assay number, the name of the depositor, the locality or source from which the ore was derived, and a brief description of the assay, including the percentage of gold and silver.
National Archives online catalog entry is https://catalog.archives.gov/id/2655903. See also the National Archives & Records Administration numismatic finding aids at https://nnp.wustl.edu/library/archivedetail/538870.
Scanned at the National Archives in Denver, courtesy of John Graffeo.