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

Release: H.4.1 Factors Affecting Reserve Balances  

Units:  Billions of Dollars, Not Seasonally Adjusted

Frequency:  Weekly, Ending Wednesday

Notes:

Federal Reserve Bank New York, on behalf of the Federal Reserve System, provides correspondent and custodial banking services for central banks, monetary authorities, and certain international organizations to facilitate their official financial operations. This item indicates the face values of marketable securities held in custody for these accounts.

This data series has been discontinued, please see series ID: https://fred.stlouisfed.org/series/WSEFINT1
Memorandum item: Securities Held in Custody for Foreign Official and International Accounts. For further information
on the changes to the H.4.1 Statistical Release please visit the following: http://www.federalreserve.gov/releases/h41