Anita in 1977 was the other "A" storm.

There have been 5 unnamed category 5 storms in recorded history, 4 of which made landfall as a cat. 5 -- 1928 in Puerto Rico, 1932 in the Bahamas, the 1935 Fl. Keys hurricane, and another in the Bahamas in 1948. Rounding out that list is one in 1938.

The list I went by is here: http://lwf.ncdc.noaa.gov/oa/satellite/satelliteseye/educational/cat5hur.html. The list itself has not been updated to include either Isabel or Ivan, the only two category 5 storms since the list was last updated, nor has Andrew been added as a category 5 storm in 1992.