I think it is B. thiemei, formerly known as B. macdougallii, rhizomatous and I think classified as 'giant leaved'. I've never grown it so don't know how it is cultivated.

What about carolineifolia? The leaves aren't quite right but close.

My thiemei doesn't look like the picture above but then I bought if from GHW and they often sell something else.

Here is a picture of one of my thiemei.

Well, according to the Smithsonian pictures,both Bs. thiemei and carolinifolia have almost identical leaves in that each leaflet is attached to the main leaf separately, and the GHW plant is not quite fully attached that way. For all I know there may be other begonias who grow that way, I am just guessing really.

That is what I was kind of thinking too Joan. I bought a crassicaulis from GHW over 15 years ago and I knew it wasn't correct but I liked the plant. I found the name of it just 3 to 4 years ago - Bayberry Lane.

The other possibility of the unknown plant above might be hemsleyana (green form) if we had any idea on the size of the leaves and plant.

Thanks so much everyone I will pass the info along