Section 24D. Every person shall keep true and accurate records of the ages of all persons employed by him, as far as practicable to do so, and shall upon demand furnish to the commissioner or his authorized representative a true copy of any such record, verified upon oath. Such records shall be open to investigation by the commissioner or his authorized representative at any reasonable time. Whoever violates any provision of this section shall be punished by a fine of not less than twenty-five nor more than one hundred dollars, and each day of failure to keep such records or to furnish such copies thereof, upon demand, to the commissioner or his authorized representative shall constitute a separate offence.