Canada #372 15c Blackish Blue Posthorn & Globe, 1957 UPU Congress Issue, Single Usage on August 28, 1957 Shortpaid Double Airmail Cover to UK, Sent Surface

A very fine shortpaid double weight 30c airmail cover to the UK, which as sent in August 1957 and is franked with a single 15c post horn stamp from the UPU Congress Issue. The cover was marked "Shortpaid for Air Conveyance" and sent surface, rather than being rated postage due. A nice single usage of this high value commemorative.

Our estimate of the value of this cover based on the above factors is $25. To understand how we have assessed the cover and arrived at this estimate and to gain a broader understanding of postal history collecting, I would suggest you read the article linked here. It should clarify the factors that make covers, and this one in particular scarce, and will help you to understand why we have estimated it at this amount.