CAFDC533re Unitrade # 533 pair. Canada Post Replacement Cover
Unitrade # 533 pair First Day Cover
Discovery of Insulin
Canada Post Replacement Cover
Ottawa, 3 March 1971
Chung / Narbonne Specialized Catalogue: R152
Beginning in 1949, first day covers forwarded to the post office in Ottawa which were damaged or lost during processing were replaced with a specially designed cover. Eight different cachet designs are known. The practice continued until 1974.