A. Federal Tax Records, 1913-1944, 32 folders. This series is arranged chronologically by tax year regardless of the particular tax involved. For most years there are the following principal record types: Corporate Tax Returns (standard forms, including those for income, profits, and excess profits taxes); Capital Stock Tax Returns; Annual Information; Returns, 1918-1930, summarizing dividend payments of $500 or more or other income payments of $1500 or more; and groups of "Working Papers," apparently used in preparing returns, including penciled sheets of calculations and attached copies of balance sheets, trial balances, income accounts, financial statements, and other documents. The corporate tax returns are often accompanied by correspondence, exhibits, and other documents. Many information returns have attached lists of names, addresses, and amounts paid.

B. Federal Tax Correspondence, 1914-1932, 2 folders. The federal tax correspondence is largely between the Hercules and members of the Day family and other partners or between the Hercules and the U.S. Commissioner of Internal Revenue and concerns distribution of dividends, the sources of dividends, the determination of tax liability of Hercules Mining Company (HMC) and of the partners, depletion allowances, personal tax returns of HMC partners and shareholders, claims for tax abatement, and whether or not there were any affiliated companies. Much of the correspondence concerns HMC's claim that, as a mining partnership under Idaho law, it should be taxed as a corporation rather than the partners bearing the whole burden.

C. Charts, 1 folder. Included are a variety of documents, many of them undated but apparently prepared for tax purposes, such as a Statement of Metallic Content and Value of Ore and Concentrates Marketed 19011912; Valuation Table of the HMC 1909-1915; Analysis of Operating Costs, Depreciation etc. 1909-1915; lists of ore shipments, 1915; lists of dividend payments for various years; worksheet of depreciation charges 1905-1917; charts of HMC ownership at different times during the partnership; Statement of Net Profits, 1919; tables of Dividend Distribution, 1913-1920; and balance sheets and financial statements. Many of these documents are typed and for many there are also penciled drafts. Similar records are often filed among the federal tax records described above.

D. Shoshone County Tax Records, 1903-1916, 1925-1929, 2 folders. The principal county tax records include: Shoshone County Tax Returns, 1903-1909, 1911-1913, and 1929; Shoshone County Final Tax Receipts, Jan. 1, 1916, issued to Hercules, Humming Bird, and related companies and concerning various pieces of real property, accompanied by a list of assessed properties for the year 1915; and receipts and correspondence from other years concerning taxes on improvements in mining claims, real estate, equipment, patented grounds, yearly net profits, and ore shipments. The folder for 1925-1929 also contains some state tax documents.