4 Pa. Code § 243.5
In the event of a subsequent return to State service of a former member whose membership has been cancelled, any reinstatement of former credited service will be without social security integration supplement credits, regardless of any supplemental coverage previously credited. Any State employe who discontinues his service and does not withdraw his total accumulated deductions and who was a member of a class of service, other than Class A, prior to March 1, 1974, shall retain his membership in that class to the date of discontinuance of such service. All service rendered thereafter will be credited as Class A service. The returning member, who has not withdrawn his accumulated deductions, shall be eligible to continue accruing SSI supplement credits only if he has returned to active membership within 6 months of his previous termination.
4 Pa. Code § 243.5