§ 418. Additional benefit authorized with respect to the city of Yonkers. Notwithstanding any contrary provision of law, the city of Yonkers may by local law, ordinance or resolution, provide a benefit of two hundred fifty dollars a month to the widow or widower, and members of the family, of retired Yonkers' police officers and firefighters who were members of the New York state and local police and fire retirement system at the time of their death; provided, however, the benefit may be paid only to survivors who were receiving benefits pursuant to Local Laws seven and eight of the city of Yonkers for the year of nineteen hundred sixty-eight on or before the effective date of this section.