Series Is Presented Here As Two Variables--(1)--Original Data, 1920-1934 (2)--Original Data, 1931-1969. Data For 1920-March 1934 Are For The Average Daily Figures For U.S. Treasury Three-Six Month Notes And Certificates. Beginning February 1931, Data Are Averages Of Weekly Rates Discount On New Treasury Three Month Bills. Data For 1920-1921 Are For Average Daily Figures For The Week Nearest The 15Th Of The Month. Data For April-June 1928 Are Based On Certificates Of Six To Nine Months Maturity. Source: Direct From The The Federal Reserve Board; Also Banking And Monetary Statistics, P. 460.
This NBER data series m13029a appears on the NBER website in Chapter 13 at http://www.nber.org/databases/macrohistory/contents/chapter13.html.
NBER Indicator: m13029a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Yields On Short-Term United States Securities, Three-Six Month Treasury Notes and Certificates, Three Month Treasury Bills for United States [M1329AUSM193NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M1329AUSM193NNBR, February 8, 2016.