A note attached to the photo reveals that the hailstone was a fake:
The instigator of the creative prank confessed many years later - after he grew up and became a prominent citizen in Pipestone County. Hail ice is milky colored and not clear.
If this hailstone had been real, its dimensions would have made it the largest ever recorded. But according to NOAA, the record goes to a stone discovered in South Dakota after a storm on July 23, 2010, measuring 8 inches in diameter and weighing nearly 2 pounds.