Hi Stephen,
I've seen both plated and painted hubs, but I don't know if there was a change over date from nickel to paint, or indeed if the finished varied from batch to batch. I guess someone would know from study of catalogues if there was variation from model to model in a particular year.
A while back I posted a photo of 340 Douglases arriving for Williams Bros in Sydney in the 1920s. If Williams told Douglas that Australian customers preferred nickel to paint (or vice versa) on their hubs, it could easily be that export bikes were finished slightly differently to home market bikes. Equally if Douglas had a batch of painted hubs in a year when they were usually plated, I'm sure they'd be put on the export bikes!
I guess that Douglas bought-in their hubs - if not from Chater Lea then from someone who made them under CL license. Does anyone know for sure?
One nice original Douglas wheel I saw recently had nickel hub, black spokes, nickel nipples and black rim. FN used the same combination on its pre-WW1 bikes and it looks very nice.
If anyone is doing a budget restoration (understandable these days), all black wheels look just fine too.
Cheers
Leon