Calvin's security code is a paper note in the Fallout 76 update Wild Appalachia.
Location[]
The note can be found at Van Lowe Taxidermy, obtainable during Lying Lowe. It is in a safe in the basement accessed by placing the strange bone in a mounted wolf head's mouth.
Transcript[]
Terminal Security Code:
aSQUATCHinSHEEPSclothing
Mission Briefing:
Operation: MARY'S LITTLE LAMB
Field Operative: BLACKSHEEP (CvL)
Handler: BO-PEEP
Fixer: BIG BAD WOLF
Site: LEWISBURG