53 Pa. Stat. § 30786
All persons, now or hereafter employed in the office of the collector of taxes, shall be permitted to join any existing retirement system in effect in the city of the second class A in which such office is located, if the city council and the board of school directors shall each agree to contribute one-half, and do contribute to the retirement fund established by the act of Assembly under which such retirement system was established, from time to time one-half each, the moneys required to build up the reserves necessary for the payment of the cities annuity of such employes upon retirement.
Upon joining any such retirement system the employes of the office of the collector of taxes shall enjoy all the rights, and be subject to all the requirements and duties, as provided by the act of Assembly under which such retirement system operates.
53 P.S. § 30786