Art,
Canada has done a number of them in the past, those were all silver dollars, but some were only 0.500 fine, others were 0.800 fine. These latest ones are all $20 face value and contain an ounce of pure silver. The series done from 2000-2003 were part of a larger transporation series, so for each year there were 4 coins, one from each mode of transport: rail, auto, sea, air. I've only pursued the rail series. The newest series is focused solely on famous Canadian locomotives, and it started in 2008, so there arer now 4 coins in that series. In the new series, the first was the Royal Hudson, then the Jubilee in 2009, the Selkirk in 2010 and the D-10 in 2011 (this was also done on the 2002 issue I just got). It's a pretty fun series!