Vault cash eligible to satisfy reserve requirements that's held by institutions not exempt from reserve requirements.
Effective February 2, 1984, reserve computation and maintenance periods have been changed from weekly to bi-weekly. Series with data prior to February 2, 1984 have different values reported from one week to the next. After February 2, 1984, the value repeats for 2 consecutive weeks.
Board of Governors of the Federal Reserve System (US), Vault Cash, Total [TLVAULTW], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/TLVAULTW, February 28, 2020.