These props came with a 1/50 metal Douglas DC-4 model I own and I was very surprised the high level of machine work detail that went into their manufacture. See the photo below
I am thinking these props and hubs on the DC-4 models is it the handy work of Douglas back in the 40s or 50s. I was impressed if someone other than Douglas went to this level of detail back in the day. The hub has a groove cut out close to the base and there are pins that go into a wood or cork type of wood that is packed into the wing section.
As I had never seen this level of workmanship on a set of props in all my years of model collecting so I decided to share this information on this forum.