Found this in my yard today... about 8 inches down. Possibly plated? Anyway, I did a little research and the League of Saint Christopher of San Juan Capistrano doesn't seem to exist anymore, but the concept of the token is pretty cool. They would register the serial numbers and you would put them on your key chain (Saint Christopher is the patron saint of travelers). If you lost your keys, and someone found them, they could drop them in any mailbox and it would go back to the League of Saint Christopher of San Juan Capistrano where they would look up the serial number and send the keys back to the registered owner.