When the shield was held in Clark Kent's hand and Dax-Ur's name was spoken, Dax-Ur's shield emitted the high pitched sound of a Kryptonian beacon and teleported him to Dax-Ur's location.
Brainiac was able to hear the sound from Suicide Slums, signifying that the beacon sound has considerable range.
The shield was brought to Earth by Dax-Ur, one of Krypton's greatest scientists. He lost it a century ago, and it somehow ended up in a time capsule buried in Smallville.
The Weather Girls came to Smallville, looking for a treasure map to a hidden time capsule. It supposedly led to millions of dollars of gold bars. They entered the "Miss Sweet Corn" beauty pageant as a distraction.