1. Original, the German thaler; hence, any of the various large silver coins resembling it described in definition 2 – 8 below.
2. The Spanish peso, or piece of eight (= 8 reals), called peso duro, or in English hard dollar, which formerly circulated widely, esp. in the Americas; also, the modern Spanish peso, or 5-peseta piece (nominally worth $.965. See PESETA)
3. A United States coin, which since 1837 has been made 412.5 grains (26.730) of silver .900 fine. Except for the design it is nearly identical with the old Spanish dollar. It was first issued in 1794. Prior to 1873, it was the monetary unit, and since then has been maintained by the government on a parity with the gold dollar. Its intrinsic value in silver at 60 cents an ounce, or at a ratio to gold of 34.45:1, is 46.4 cents. It is legal tender for any amount.
4. A United States coin similar to the above but weighing 420 grains, issued for use in Oriental trade and called specifically trade dollar. It has not been coined since 1887.
There are no statutes that have changed the original definition of a "dollar."