It is unique among Amaryllis, and has a grace unlike modern varieties. I love the green throat too. I wonder if its a species?
I was trying to think how old it must be, considering the lady who gave it to me, had inherited it from her aunt. She had inherited the house, its contents, and the land, around 1980. The previous owner was in her late 90s when she passed, and she had lots of very well established perennials, house plants, and old Dahlia varieties she had dug every year...yes, right up till the end!
I believe that tub of bulbs had to be at least 50 years of growth, and probably older.