Well it looks like this wheel (in the post above) is not Douglas, despite the similarities in the hub layout.
The advice I have is that up to and including 1912, hubs were from Chater Lea, and from 1913 on the Douglas hubs (which are very close in design to the Chater Lea hubs they replaced) are all either identical or very similar right through until the mid 1920s.
Still on hubs, I found this one in a pile of Douglas bits I have been sorting through. It has screw-on dust covers on both sides. I assume it dates from the mid 1920s?
Sorry about the chrome - it wasn't me! I'm not sure if these late hubs had Douglas stamped on them originally, but if this one did the plater has removed it.
Does anyone need it? If so, please make an offer. I'll put it on the "parts for sale" board. (Added Sun 19 Aug: I've had a couple of offers so it looks like the hub is sold.)
Leon