According the editors of the 1999 edition of the Unitrade Specialized Catalogue of Canadian Stamps approximately 400 copies of the
Seaway Comemorative were issued with inverted centres. There are fourteen recorded covers or cards with this error properly used.
This “fake” was probably intended as a prank: the unlikely placement of a regular stamp beside an invert is the first clue that this is not real.
Bileski, Kasimir, et. al. UNITRADE Specialized Catalogue of Canadian Stamps 1999. Toronto: The Unitrade Press, 1998.
"Canada." Standard Postage Stamp Catalogue. 1997.
Molson, Kenneth M. Canada's National Aviation Museum. Ottawa: National Museum of Science and Technology, 1988.