25 U.S.C. § 161b
All tribal funds arising under section 155 of this title on , included in the fund “Indian Money, Proceeds of Labor”, shall, on and after , be carried on the books of the Treasury Department in separate accounts for the respective tribes, and all such funds with account balances exceeding $500 shall bear simple interest at the rate of 4 per centum per annum from .
(Feb. 12, 1929, ch. 178, § 2, as added June 13, 1930, ch. 483, 46 Stat. 584.)