Level from the H.4.1 Federal Reserve statistical release, table 8 Consolidated Statement of Condition of All Federal Reserve Banks, Other assets denominated in foreign currencies. While data is released weekly (Wednesday), we use only quarter end dates. Unadjusted flow is calculated as 50 percent of rest of the world official foreign currency holdings (FOF series FU263111503). Data for the most recent ten years show no significant seasonality.