John,
i have a complete set of those as well! Mine came from a Canadian school teacher. She received them from a dealer in the early 1970s to use in her classroom to teach Canadian Ag History. Her father was friends with the dealer. They are in mint condition. I doubt if they were ever used!!
So to answer your question - I can only assume they were distributed in Canada. Not many of them in the States so I assume they did not come into the US!
Gary