53 Pa. Stat. § 23653.1
Each person who shall become an employee of the Bureau of Police, after having been employed by the city other than in the Bureau of Police, and who shall desire to have such previous service counted for eligibility to receive a pension under the provisions of section 13 of this act, shall be required to pay to the fund an amount equal to five per centum (5%) of his or her total salary or wages theretofore received by him or her, for each previous month of service for which he receives credit as an employee of the city, with interest at the rate earned by the fund during the period of such prior employment: Provided, That service to be credited which was performed after the effective date of this act shall be paid for at the new rate of contribution. Full payment of such amount shall be a condition precedent to the member receiving credit for all or any part of said period of previous service for eligibility to receive a pension. Such amount shall be collected from the monthly salary or wages of the member over the period of two years in the manner provided in clause (1) of section 10 of this act, or in such manner and period as the Board of Managers may determine. If, however, any such member shall be injured in the line of duty before he shall have made such full contribution for past service, so long as the disability continues he or she shall be eligible to pension under this act, but any amount which he or she shall not yet have paid to the fund as a contribution for past services under this section at the date of his or her injury, shall be paid, if the board, in its discretion, shall so determine, in such monthly payments as the board may determine, which amounts shall be deducted from his or her pension as and when monthly payments thereof shall be made.
53 P.S. § 23653.1