Source : Webster's Revised Unabridged Dictionary (1913)

Seven-thirties \Sev`en-thir"ties\, n. pl.
   A name given to three several issues of United States
   Treasury notes, made during the Civil War, in denominations
   of $50 and over, bearing interest at the rate of seven and
   three tenths (thirty hundredths) per cent annually. Within a
   few years they were all redeemed or funded.