A. Monthly Reports on Plant Maintenance, Apr. 1930-May 1931, 1 folder. Describing the condition of electrical and mechanical equipment.

B. Proposals for Installation of Equipment, 1902-1903, 1 folder. Includes correspondence with the California Wire Works concerning construction of a tramway; with Pelton Water Wheel Company regarding pipelines; and with Allis-Chalmers Company for iron work. There are also blueprints, drawings, and receipts.

C. Cost Records, 1910-1916, 1 vol. and 1 folder. A loose-leaf notebook containing descriptions of mill, hoisting, and other equipment, with the cost, usually including shipping charges for each item, invoice dates and numbers. Inserted in a pocket were typed lists and a few clippings giving costs of number 5 shaft construction; names of owners, addresses, dates, and acreage for various mining claims; annual, or sometimes monthly statistics, generally covering 1901-1912, on dividends, smelter returns and deductions, ore milled and shipped, wages, employees, and taxes paid.

D. Voucher Registers, 1916-1947, 9 vols. Voucher registers record basic information from the voucher, such as date, summary description, voucher number, amount of transaction. Registers also record the distribution of credits and expenses among various accounts. This series covers Hercules vouchers no. 313 to no. 21,252. The vouchers themselves, in 187 binders and measuring 62-1/3 lineal feet, have been discarded as the Voucher Registers and the Invoice Records described below provide an adequate summary.

E. Voucher Registers of the Hercules Mill, 1941-1947, 2 vols. The Voucher registers of the Hercules Mill provide a detailed distribution of credits and expenditures which the general Voucher Registers described above simply lump into a "Mill Balance Account." These mill accounts constitute the majority of the entries in the general voucher registers during this period; they may be identified in the ledger of the Hercules Mill, 1941-1947, listed above under Accounting Records.

F. Invoice Records, 1916-1928, 3 vols. These volumes identify the items purchased, distributed in columns alphabetically, give "filing number" (i.e., invoice or voucher number) for each transaction, date of invoice, name of the other party to the transaction, and the subject of the transaction. The Invoice Record is sometimes more complete than the Voucher Register, including some voucher numbers missing from the corresponding register.