Source : Webster's Revised Unabridged Dictionary (1913)

Doubloon \Doub*loon"\, n. [F. doublon, Sp. doblon. See {Double},
   a., and cf. {Dupion}.]
   A Spanish gold coin, no longer issued, varying in value at
   different times from over fifteen dollars to about five. See
   {Doblon} in Sup.

Source : WordNet®

doubloon
     n : a former Spanish gold coin