N.J. Stat. § 18A:66-5
The retirement system shall classify the members in such groups by age as it may determine for actuarial purposes.
The system shall further classify the membership by benefit rates as class A or class B members, as follows:
"Class A" shall include those members who contribute to the annuity savings fund at a per centum salary, computed to be sufficient, with regular interest, to procure for the member, one retirement for service, an annuity equal to 1/140 of his final compensation for each year of service as a member.
"Class B" shall include those members who have elected or who shall hereafter contribute to the annuity savings fund at a higher rate per centum, computed to be sufficient, with regular interest, to procure for the member, on retirement for service, an annuity equal to 1/120 of his final compensation for each year of service as a member.
Any member on December 31, 1955, may by his election contribute to the retirement system at the rate of contribution applicable to class B members of the public employees' retirement system as of January 2, 1955, based upon the member's age when he last became a member. He shall thereafter be classified as a class B member. Any such member may elect to increase his accumulated deductions by the amount deemed necessary by the board of trustees on the advice of the actuary in order to receive credit as a class B member for all or part of his service prior to the date of such election. The board of trustees shall establish the necessary rules governing the election by members of class B credit for all service.
Any member on December 31, 1955, who is not a veteran and who does not elect to receive class B credit for all or any portion of his service shall receive credit as a class A member for all service not credited as class B service. Any such member who does not elect class B membership shall contribute at the rate of contribution initially certified to him upon his last becoming a member; provided, however, that any such person who became a member after June 30, 1946, shall have his contributions on and after January 1, 1955, based on the rates of contribution applicable on June 30, 1946, for his age at the time he last became a member.
N.J.S. § 18A:66-5