Thank you, Kai, for your excellent explanation that reflects many years of experience and understanding. This is my first vintage bike restoration project. I am now in the assembly stage. All seems fine but this double locknut was unusual and thus I wanted to ask in this forum. I completely dis-assembled the bike and replaced all hub and wheel bearings and greased with the green Phil Wood grease. I am using loose bearings everywhere including the headset. Below is a photo of the current condition. Thanks again.