One identification sign not exceeding 20 square feet in area for a place of worship, parish house, religious school building, hospital, nursing home, private school or apartment building or other special permitted use. Such sign shall refer only to the premises upon which it is located. Such sign shall not be located in a required yard unless affixed to the wall of a building, except that in no case need it be located more than 25 feet from the street line. Notwithstanding the above, a bulletin board of a place of worship not more than 12 feet square may be placed no closer than 10 feet to a street line.