Simon Bolivar, a Tomas agent, wanted to hide a clue in South America after it was free from the Spanish. He helped organize a revolution and helped the Spanish colonies to become independant. He then hid this clue in Venezuela. However, Bolivar was extremely protective of this clue and wanted it to always be close to him. He arranged for the clue to be kept close to his corpse after he died which is why the clue was located in the National Pantheon in Venezuela.
The box that held the clue mace was lined with lead so that it could not be x-rayed.
Lead is a metal that used to be used in pencils. However, after realizing that lead is poisonous, it was replaced with graphite.