Consisting of but one metal; specifically, comprising coins that consist of but one metal (or alloy), as gold or silver: as, a monometallic, currency.

What do you mean by Monometallic?

1 : of or relating to monometallism. 2 : consisting of or employing one metal.

Which countries were using Monometallic standard?

history of the gold standard

…but in the 1870s a monometallic gold standard was adopted by Germany, France, and the United States, with many other countries following suit. This shift occurred because recent gold discoveries in western North America had made gold more plentiful.