It looks like a Greg Sytch hybrid. I had his Kissimmee begonia a few years ago which is close to this, but without the curl.

Try this link and see what you think.

https://www.pinterest.com/pin/36591815701913032/

the Italian site

sells 'Guinevere' (syn 'Black Taffeta'). So may be that's what it is? Although it is not as black; but then in South FL light it is prolly darker.

TerraNova nurseries lists it too, but it has very pronounced light green veining...of course i didn't check the veining (was hidden in the curl) or the undersides color.

It is a very showy combo of large feathery crinkled black curling leaves. The plant itself is huge!

It dropped some seedpods, very wet and not dry yet. so don't know if they are ripe or viable. I never sprouted begonia seeds, am tempted to try :). How soon they sprout for rhizomatous? i can try to sprinkle them on slightly moist sphag in closed plastic clam shell. Unfortunately i left them to dry in seedpods on the table and then forgot them, so have to wait till June to try.

That sounds like a stunning Begonia! B. ‘Black Fang’ or B. ‘Dark Mambo’ might be worth looking into—both have dark, dramatic foliage with interesting textures. A photo would help with a more accurate ID!

i looked at pics of both, of course: 'Black Fang' i grew myself, it has a very different leaf type with prominent white veining it's not even close to my pic.

'Black Mambo' curls and is star shaped, but the leaves are smooth and don't have overlap or crinkle. They also say it has pinkish flowers.

The one i posted has white flowers. I see euro-sites offering B. 'Black Taffeta' for sale, it matches well with my pics of it, so i'm quite convinced.