N.J. Stat. § 43:10-29.3
Any county detective employed in the office of the prosecutor of the pleas, of any county now or hereafter having a population of more than three hundred thousand and not more than five hundred thousand inhabitants, who, at the time of his entry into service as a county detective, had not attained the age of fifty years and who is not a member of the pension fund for county detectives of said county and who signifies in writing his desire to become a member of said pension fund to the board of chosen freeholders of the county within six months after the effective date of this act may be admitted as a member of said pension fund, if approved by the board of chosen freeholders, with the same standing as a member of said fund as if he had joined it upon his entry into such service as a county detective; provided, (a) that he satisfies the board of chosen freeholders that he meets the conditions required under this act; (b) that he shall pay into said fund all accrued contributions, with interest, either in one payment or in regular semi-monthly payments, under such rules and regulations as the board of chosen freeholders shall make; and (c) that he consent to the regular deductions required of other members of said fund.
N.J.S. § 43:10-29.3