This is a magnetic small. It is hidden on the diode. A diode is for preventing rust on all the underground metal structures. Oscar zero is a decommissioned missile command center. For more information and hours visit http://www.oscarzero.com/ and visit https://www.history.nd.gov/historicsites/minutemanmissile/index.html. This is a very cool place to visit if you have extra time.
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