No person shall be excused from testifying or from producing books, accounts, and papers in any proceeding based upon or growing out of any violation of the provisions of this chapter, on the ground or for the reason that the testimony or evidence, documentary or otherwise, required of him may tend to incriminate him or subject him to penalty or forfeiture; but no person having so testified shall be prosecuted or subjected to any penalty or forfeiture for or on account of any transaction, matter, or thing concerning which he may have testified or produced any documentary evidence: Provided, That no person so testifying shall be exempted from prosecution or punishment for perjury; Provided further, That the immunity hereby conferred shall extend only to a natural person who, in obedience to a subpoena gives testimony under oath or produces evidence, documentary or otherwise under oath.