N.J. Stat. Ann. § 43:10-37

Any county police officer who has honorably served for a period of twenty years in a duly organized county police department of any county of this state, having a population in excess of two hundred thousand and not more than four hundred thousand, and has reached the age of fifty years, shall, on his own application, be retired on half pay. A member of such county police department who has honorably served for a period of twenty years and reached the age of sixty-five years shall be retired on half pay.