This is one of the four "laminadoras," enormous machines used to flatten silver ingots into thin sheets from which coins were struck. The laminadoras were driven by mules in the room below. Working life of a mule was three months. Legend has it that the Spanish used mules because the slaves did not live as long. Potosi, Bolivia 2000
(Trivia - Bolivia no longer has a mint. It imports all coinage.)