In the Canadian Postal history, this St Lawrence Seaways Invert stamp is the best-known error stamp. This stamp was issued to commemorate the opening of the St Lawrence Seaway in 1959, this seaway enabled large ships to navigate from the Atlantic to the Great lakes.
The St Lawrence Seaway stamp is the first significant error stamp of the Canada Post, it depicts the Seaway inverted in the centre. There are approximately 200 copies of this stamp known today. One of its specimens was sold for 13,500 dollars. The mint examples of this stamp are said to be auctioned for more than 16,000 dollars.
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