Looks like it’s time for me to join the conversation. The “thimble”, in Budd literature, is termed a “Dual Cap Nut” or just “DCN”. Left hand threads on the left, right hand threads on the right.
That front hub is a Marmon-Herrington, and I’m guessing the truck is either a SnoGo or a 1953 M254. M-H would have mounted wheel spacers on the front axles of each of these which would have needed the DCNs to hold them in place. You’ll find the normal 3/4”-16 tpi wheel stud inside the DCN. I have a spacer set I pulled from a ‘53 parts truck. A normal M-H wouldn’t have needed these on the front, only on the rear.
The yellow paint makes it more likely we’re seeing a SnoGo, maybe pre 1948 judging by the (am I seeing 18”?) locking side ring style wheel. The 1953 M254s (F-250s) used the spacers because M-H used up old spec parts when new models were introduced by Ford. Early ‘53s have the 1952 and earlier 5 x 8” pattern hubs while late ‘53s have the 6 x 7.25” hubs.
If you are parting this truck out, and if I’m right that I’m seeing 18” wheels, I will have interest in them. Stu