Section, added Pub. L. 85–866, title II, § 206(a), Sept. 2, 1958, 72 Stat. 1681, 6166; amended Pub. L. 93–625, § 7(d)(2), (3), Jan. 3, 1975, 88 Stat. 2115; renumbered 6166A and amended Pub. L. 94–455, title XIX, § 1906(b)(13)(A), title XX, 2004(a), Oct. 4, 1976, 90 Stat. 1834, 1862, provided for an extension of time for payment of estate tax where estate consists largely of interest in closely held business.