N.J. Stat. § 43:16-12
In any municipality in which this subtitle has taken effect under section 43:16-10 of this title, if before this subtitle became effective a paid fire department had not been regularly constituted and organized by ordinance of the governing body thereof, but firemen were employed on regular twenty-four-hour duty for pay and two per cent was deducted from every payment of salary to them and the sums so deducted were theretofore paid into a pension fund for their relief, and upon the taking effect of this subtitle in such municipality, these sums were added to the pension fund provided for in this subtitle; and where the governing body thereof continued to deduct from every payment of salary to such paid firemen two per cent of the amount thereof and credited same to the pension fund; and where, prior to March eleventh, one thousand nine hundred and twenty-four, a paid fire department was thereafter constituted and created in the municipality in the manner provided by law, and all such paid firemen were thereupon appointed to the paid fire department, the age of the paid firemen shall, for the purposes of this subtitle, be reckoned as of the time they were first employed for regular twenty-four-hour duty for pay, and the years of service rendered by them shall, for the purpose of this subtitle, be reckoned from the same time, and not from their reappointment after the creation of the regular paid fire department.
N.J.S. § 43:16-12