N.J. Stat. § 43:13-22.1
Notwithstanding the provisions of section 43:1-1 of the Revised Statutes, any employee of a city of the first class as defined in the article to which this is a supplement who at the time of the adoption of this act is ineligible to membership in the pension fund established for employees of said city of the first class by chapter one hundred ninety of the laws of one thousand nine hundred and twenty-seven or article two of chapter thirteen of Title 43 of the Revised Statutes by reason of having accepted employment after reaching the age of forty years and who was at the time of accepting such employment under the age of fifty years, or any person now in the employ of a city of the first class, who was in the employ of said city on, or who has accepted employment by said city since March twenty-eighth, one thousand nine hundred and twenty-seven, who has remained continuously in the employ of said city and who was at the time of accepting such employment eligible to membership in the pension fund established for employees of said city of the first class by chapter one hundred ninety of the laws of one thousand nine hundred and twenty-seven or article two of chapter thirteen of Title 43 of the Revised Statutes but who declined to join said pension fund, may within two months after this act becomes effective become a member of such pension fund by payment into the fund, in such manner as shall be determined by the pension commission, of all arrears, with interest, as the pension commission shall determine to be due in order to give such employee the same standing as a member of said fund, in the case of employees employed on March twenty-eighth, one thousand nine hundred and twenty-seven, as all other members who joined said pension fund when the law providing for such fund became effective, and in the case of employees accepting employment since that date, as if such employees had joined said fund upon accepting such employment, in which case the maximum rate of interest shall not exceed the average rate of earnings of the investments of said fund and the maximum length of time for the payment of arrears shall be five years from the date of the application to join the fund.
N.J.S. § 43:13-22.1