It's a BSA Hublite, not a Sturmey Archer Dynohub. It is pre-Raleigh which dates it to no newer than 1957 and apparently pretty rare. Some of my Brit pals who grew up there in the 50s never saw one. This one does work. What little I have learned about it is that it was capable of pushing a 6v 2.4w lamp to full brightness at 4mph. My SA dyno could barely generate a glow at that speed until converted it to run LEDs.
Now I just need to build a BSA around it.