Nor is the mystery the number of stamps in it.
Reportedly 4,655,000 in one solid — not hollow — ball. All cancelled.
The mystery is not its location.
It’s the centerpiece of the Leon Myers Stamp Center at Boys Town in Nebraska, the child care agency founded by Father Flanagan, whom Spencer Tracy personified in a 1938 film.
And there’s no mystery about who made it.
That would be the members of the Boys Town Stamp Collecting Club who began in 1953 and finished in 1955. Apparently, they had a lot of time for hobbies.
No, ultimately, the mystery for me is WHY they devoted two years to layering over four million stamps into Planet Postage. I guess it’s a more lasting result than if they had spent their time playing Parcheesi or Capture the Flag.