Silo Charlie code pieces are dynamically changing notes in Fallout 76.
A small device displaying one of eight parts of a nuclear launch code in bright nixie tube lettering. The red "SILO CHARLIE" label indicates the piece is part of the launch code for Site Charlie.
Eight different code pieces exist, with the characters of each changing every week. Code pieces expire weekly on Monday, no matter when they are acquired.
Player characters with a code piece will get a notification before expiration, indicating they will soon expire and be removed from the inventory.
Silo Charlie code pieces can be found on both scorched officers and feral ghoul officers.
Player characters can complete the repeatable Hide and Seek and Destroy quest to pinpoint the location of code pieces around the map.