Said board, or any member thereof, may enter any establishment in which a strike or lockout exists in order to examine payrolls and other records and to inspect conditions affecting the relations between employees and employers. Said board, or any member thereof, may summon, by subpoena, employers, employees or any other persons whose testimony may be pertinent to the matters before said board, together with any records or other documents relating to such strike or lockout. In case of contumacy or refusal to obey a subpoena issued to any person, the Superior Court, upon application by the board, shall have jurisdiction to order such person to appear before the board to produce evidence or to give testimony touching the matter under investigation or in question, and any failure to obey such order may be punished by said court as a contempt thereof. No person shall be excused from attending and testifying or from producing books, records, correspondence, documents or other evidence in obedience to the subpoena of the board, 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 individual 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 individual so testifying shall not be exempt from prosecution and punishment for perjury committed in so testifying. In case of a dispute which has not reached the stage of a strike or lockout, said board, upon the request of either party to the dispute, is authorized to exercise the same powers and perform the same duties as in case of a strike or lockout. Said board, or any member thereof, shall have the power to take testimony under oath and to administer oaths.