Buckles are not a running thing. They are a horse trail racing tradition. Which makes sense. Horseback riders wear belts.
Western States was originally a horse trail race. Over the years it was attempted a couple of times on foot. In the early 70’s a group of soldiers marched it, In 1974 Gordy Ainsleigh famously did the race on foot to see if it could be done in under 24 hours.
A couple of years later Ken “Cowman” Shirk did it in over 24 hours.
It was not until 1977 the first “Western States 100” was held as a formal race.
For a while the two races were held i conjunction, until the foot version became too large to coexist with the Original horse event.
The foot version shared a couple of features of the horse race. First; “100 miles” was not a precise measurement. In horse lingo it meant “Really Long Ride”. As opposed to “50 miles” which simply meant “Long Ride.” And the second was picked up at some point, the awarding of a fancy belt buckle for breaking 24 hours.
After the two races split, there were changes made. The course actually measured, and found to be considerably short of “100 miles” as a measured distance. There were a couple of lengthenings before the course was finally extended to what is about as accurately 100 miles as you can get on a trail. And the buckle somewhere along the way was extended to 30 hours, with a nicer buckle for sub 24.
The buckle was adopted by other ultra events as a nice prize almost immediately. By the time that Western States was actually 100 miles in length, I had already received a buckle at a 50km race, and I had been wearing my Vol State buckle for years. The association of a buckle as denoting the completion of a 100 mile run is imaginary history created after the fact. It came into being as just a premium award for races of any distance. The meaning of the buckle to the recipient is the same as any award. The harder you work for it, the more it means.