53 Pa. Stat. § 22585
All clerks and employes employed in the office of the collector of delinquent city taxes, abolished by ordinance pursuant to this act, shall be transferred to and become employes of the city treasurer's office. All such clerks and employes shall become eligible to membership in the retirement system established for city employes, and shall be entitled to receive credit in the retirement system as city employes for all years of service in the office of the collector of delinquent taxes upon payment into the retirement fund of a sum equal to the amount such persons would have paid into such fund, if they had joined the retirement system at the time the same was established if them employed in the office of the delinquent tax collector, or if employed first at a later date then a sum equal to the amount such persons would have paid into such fund from the time they were first so employed.
53 P.S. § 22585