The Collaborative International Dictionary of English v.0.48:

Stater \Sta"ter\ (st[=a]"t[~e]r), n. [L. stater, Gr. stath`r.]
   (Gr. Antiq.)
   The principal gold coin of ancient Greece. It varied much in
   value, the stater best known at Athens being worth about
   [pounds]1 2s., or about $5.35 (in 1890 value). The Attic
   silver tetradrachm was in later times called stater.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Tetradrachm \Tet"ra*drachm\, Tetradrachma \Tet`ra*drach"ma\, n.
   [NL. tetradrachma, fr. Gr. tetra`drachmon; te`tra- (see
   Tetra-) + drachmh` drachm, drachma.]
   A silver coin among the ancient Greeks, of the value of four
   drachms.

   Note: The Attic tetradrachm was equal to 3s. 3d. sterling, or
         about 76 cents.
         [1913 Webster]