It's a very rare pattern coin struck at the Tianjin mint in 1929.
The obverse has a portrait of Sun Yat-sen with the inscription "Republic of China 18th Year" (1929) at the top.
The reverse side has the denomination one yuan ("one dollar").
Unfortunately, your coin is a poorly-made reproduction.
Chinese coin collectors consider this 1929 pattern coin as "one of the twenty rarest silver coins" and authentic specimens sell for several hundred thousand of US dollars.
Gary