Source: Board of Governors of the Federal Reserve System (US)  

Release: H.4.1 Factors Affecting Reserve Balances  

Units:  Millions of U.S. Dollars, Not Seasonally Adjusted

Frequency:  Weekly, As of Wednesday

Notes:

Treasury cash holdings include paper currency and coin held in Treasury vaults, including silver bullion, silver dollars, coinage metal, and unmonetized gold. The value of Treasury cash holdings is estimated using Treasury data.