The Collaborative International Dictionary of English v.0.48:

thaler \tha"ler\ (t[aum]"l[~e]r), n. [G. See Dollar.]
   A former German silver coin worth about three shillings
   sterling, or about 73 cents, around 1900.
   [1913 Webster +PJC]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

THALER. The name of a coin. The thaler of Prussia and of the northern states
of Germany is deemed as money of account, at the custom-house, to be of the
value of sixty-nine cents. Act of May 22, 1846.
     2. The thaler of Bremen, of seventy-two grotes, is deemed of the value
of seventy-one cents. Act of March 3, 1843.