St. Lawrence Seaway Invert (1959 Canadian stamp error)

The St. Lawrence Seaway invert is an error of Canada's 5-cent St. Lawrence Seaway stamp, issued on June 26, 1959 as a joint issue with the United States for the opening of the Seaway. On the error, the blue central vignette is printed upside down. The first report came from Winnipeg in August 1959, and about 400 examples are known.

Text from OyList