No person shall be excused from attending and testifying or from producing documents or other evidence in obedience to the subpoena of the administrator, or of any duly authorized officer or agent thereof, on the ground that the testimony or evidence required of him may tend to incriminate him or subject him to a penalty or forfeiture, but no person shall be prosecuted or subjected to any penalty or forfeiture for or on account of any transaction, matter or thing concerning which he is compelled, after having claimed his privilege against self-incrimination, to testify or produce evidence; except that such person so testifying shall not be exempt from prosecution and punishment for perjury committed in so testifying. The immunity herein provided shall extend only to natural persons so compelled to testify.