Perhaps Lelands had the most plausible description back in 2003?
"2” gold pendant is like the one used to label the most famous locker at Yankee Stadium, home to the great Bambino’s spikes, glove, & uniform. Tag is EX. Engraved with “Babe Ruth 3” on one side, “Yankee Stadium Locker 3 The Bronx, New York” on the other.
This is believed to have been produced after Ruth’s career. Possibly given out by the Yankees as some sort of keepsake."
http://www.lelands.com/auction/Aucti...uth-Locker-Tag