Most of the papers in this record group were in labeled file folders or three ring notebooks, but were in no discernible order. Therefore, while folder and notebook headings were retained, a series order was imposed during processing. The folders in each series are in alphabetical order and the original order of the material is maintained throughout.

The first series contains material concerning the overall organization of the division, including budget manuals, policies manuals, supervisors manuals, and work rules.

The second series, or research files, is divided into two subseries, one is the material that was originally in file folders, the second is the material originally contained in notebooks. Most items in this series deal with the operation of the plant, and various experiments performed. There is a section on patent applications, and a list of patents held by the company.

The Washington Water Power rate increase requests are arranged by case number. Included are petitions and other legal documents, transcripts of testimonies, and occasionally legal documents from court cases resulting from the application.

The final series contains blueprints of the lead and zinc plants, aerial views of the zinc plant and smelter, a University of Idaho thesis, flow sheets, and two visitors registers.

Annual reports of the Bunker Hill Company, and the session papers of the American Mining Congress were removed from the collection and sent to the library's gift receiving office for possible cataloging into the library's main collection. Suppliers catalogs, annual reports from other companies, and duplicate materials were discarded. Material from notebooks was transferred to file folders. By these means the bulk of the records was reduced by 7 cubic feet.