Denver Mint records scanned at the National Archives (NARA) in Denver - covering the period 1926. Record group 104.  Information resource name and date range: “Refinery Work Book, ca. 1926.”  Courtesy of John Graffeo.  

NARA description: This series consists of volumes that are work books used by refiners in preparing precious metals for use in coin production. The volumes record weights, calculations, and volume of gold and silver.

NARA catalog entry: https://catalog.archives.gov/id/2789168.