I finally came across a good brass hub fan, I've been using the later 1917 fan. Originally were the brass hubs painted black? I'm sure they were, so then it would be impossible to tell the brass from steel hubs. I see pictures of the pretty brass hubs with black blades.
I think just the blades were painted on the brasshub fans.
If you look more closely, you will notice the front part of the hub on a brass fan is shaped differently than a steel one.
I have an extra early brass hub I would sell if anyone needs one.