You have an interesting find there because in 1989 for the 25 cent, the change-over occured around the 0.9m range (from black to red) however, there exist some replacement within that series in which the serial number carry a different style. Perhaps yours is a replacement note??
As for the S prefix 5 cents, you can find that prefix on the 1985 5 Cent Gas coupons and on the 1972 (50th Anniversary issue) of the store coupons. In either case they are all regular issued notes, but the 1972 series is scarce but that goes for all the notes from 1972.