Looks more like Lucerna. I wondered if Argenteo-guttata and Lucerna have some common ancestor?

I can't find a picture of mine but a better example is the one I took a picture of at the FWBG Begonia Species Bank a couple of years ago.

Yes, the Species Bank photo matches that in the Thompson and Chevalier books. I don't think I have ever seen B. 'Lucerna' (as comon as the name seems to be). The description in the old Chevalier book says it has been around since 1910 and the leaf is more or less heavily spotted. I remember a name for a cane which seemed well known in the Begonia Society which had the nickname 'Trout Leaf' begonia, apparently named for its spots, Possibly that was 'Lucerna' as well. . .

Lucerna is an oldie but goodie, excellent pass along plant. Our first begonia as a pass along plant and only known as 'Angel Wing Begonia' as most canes are known as. Trout Leaf Begonia is a common name for 'Medora' and that is how I bought it a long time ago - Trout Leaf Begonia and learned the true name many years later on, just like Lucerna.

'Medora' aka Trout Leaf Begonia

'Corallina de Lucerna' with the smaller leaf 'Cracked Ice' behind it.

And a very well grown specimen at WPB convention. I hate the dim lights at the conventions where it is hard to get a good picture.