53 Pa. Stat. § 881.202
On the effective date of this act all of the assets and liabilities of the Municipal Employes' Retirement Fund shall be transferred intact to the Pennsylvania Municipal Retirement Fund. The rights and benefits of the members and of the municipalities which have joined the Municipal Employes' Retirement System shall not be impaired in any way as a result of this transfer. Likewise, the obligations and responsibilities of both the members and the member municipalities which have joined the system shall not be changed and the contractual arrangements as they existed at the time the municipalities joined the Municipal Employes' Retirement System shall continue in force. Prior service credits for any members so transferred shall be computed from the date on which the municipality joined the Municipal Employes' Retirement System.
53 P.S. § 881.202