From -- http://www.2-clicks-coins.com/article/rare-canadian-coins.html
Apart from silver dollars, Canada also used to mint silver coins of five-cent denomination. They were sometimes called “fish scales” for their thinness. In 1921, the last silver five-cent coins were struck before they were replaced with nickel cents in 1922.
Most of the 1921 Canadian five-cent coins were melted down during the change in coinage and only about 400 specimens are left, to date, making the 1921 Canadian five-cent one of the rarest Canadian coins.
Here it is.