The Treasure Vault Mining Company was organized on October 17, 1906, by George Champagne, Charles M. Johnson, Hugh Ross, Eugene R. Day, and George Miner. In 1914 the first assessment of 2 cents per share was levied in order to pay for development work. Directors of the company changed periodically; by 1925 they were Jos. A. Brown, W.B. Heitfeld, W.A. Devan, P.J. Maggy, and George Miner. The property was located on Nine Mile Canyon in the Placer Center Mining District of Shoshone County, Idaho.
Records for the stockholders meeting in 1933 showed Henry L. Day owning 1,000 shares of Treasure Vault stock. In that year he was elected to the board of directors along with George Miner, R.W. Anno, S.F. Heitfeld and W.B. Heitfeld.
A report written for the company in 1939 showed that prospecting and development work consisted of three tunnels and one shaft. The upper tunnel, a short one, was caved, as was the middle tunnel, about 300 feet in length. The lower tunnel was open and about 200 feet in length. All tunnels were drifts on the Treasure Vault Vein. The workings of the lower tunnel indicated that the vein at this point, although generally quite strong, was in places broken up and split into several parts. It was unlikely sufficient quantities of ore would be found to make continued mining profitable.
In 1945 three more mining claims, Big, Little, and Keith, were located and an assessment of 1 mill per share was levied to cover the cost of surveying and locating these claims.
On June 18, 1947, the directors met to consider and approve the plan to consolidate the Treasure Vault, Hercules, Tamarack & Custer, Dayrock, Sherman Lead, Monitor, Happy Day, Duluth, King, Stanley, WestrnUnion and Crystal Lead companies to form Day Mines, Inc. At this time the property consisted of four patented and three unpatented claims, with approximately 740 feet of development work done.