43 Pa. Stat. § 114
Whenever any female shall be employed or permitted to work in, or in connection with, any establishment, before the hour of six o'clock in the morning or after the hour of nine o'clock in the evening of any day, who, in the judgment of the Secretary of Labor and Industry or his authorized representative, is under eighteen (18) years of age, such representative of the department may demand from any person employing or permitting any such female to work in, or in connection with, his establishment, that such person shall either furnish to such representative of the department within ten days satisfactory evidence, such as shall be required by law for the issuing of employment certificates to minors that such female is, in fact, eighteen (18) years of age or over, or shall cease to employ or permit such female to work in, or in connection with, such establishment, before or after the hours above named.
In case such employer shall fail to furnish to said representative of the department, within ten days after making such written demand, the required evidence of age, and shall thereafter continue to employ such female, or permit her to work in, or in connection with, such establishment, before or after the hours aforesaid, proof of the making of such demand and of failure to produce the evidence required shall be prima facie evidence of the illegal employment of such female, in any prosecution brought therefor.
43 P.S. § 114