Looks more like Selph's Mahogany to me. Here is one of mine under a great fuchsia 'Gartenmeister' and a purple euphorbia (cotinifolia).

Your Selph's is a dead-ringer for mine, I don't think there's any doubt of that ID. I appreciate your expertise. I see at ABS that it was never registered, I'll check Thompson's book for info when I get home later. I remember Selph's from when I had a major collection in the early 80s, but not sure I ever actually grew it. I do admire the pics of Caribbean King, now to find a source for it.

Thanks again,
Russ

I found a comment on a website saying Selph's was hybridized in the 1970s, but it's not mentioned in Thompson's 1981 book Begonias. Neither is Caribbean King, which I assume is a newer hybrid. So far I've found 3 hybrids in an apparent Caribbean series. I used to have Caribbean Queen but lost it two years ago, it had lobed green leaves that were on the hairy side.

I bought this begonia this past summer at a local landscape nursery, I'm assuming it's heracleiifolia but don't know the variety.

Russ

So many hybrids that it makes my head swim. HA!

Caribbean Queen is larger than the King (at least my experience was that way). There is also C. Prince and Princess and C. Clown(?) if I remember right.

https://www.begonias.org/Articles/Vol69/Sisters.htm

http://www.begoniahouston.org/hkey/hsubkeys/hclass4449.htm

Here was my C. Queen in early Oct, 2005 after buying a gallon pot of it at PHOE early May. This is an 18 inch pot. Guess it liked the sun?