Dealers in tax-exempt securities

In computing the gross income of a taxpayer who holds during the taxable year a municipal bond (as defined in subsection (b)(1)) primarily for sale to customers in the ordinary course of his trade or business— For purposes of subsection (a)— The term “municipal bond” means any obligation issued by a government or political subdivision thereof if the interest on such obligation is excludable from gross income; but such term does not include such an obligation if— when it is sold or otherwise disposed of by the taxpayer— The term “cost of securities sold” means the amount ascertained by subtracting the inventory value of the closing inventory of a taxable year from the sum of—