A cover bearing the Nova Scotia 1851 1/- cold violet pair is valued at $50,000-75,000 at Spink.
It will star in the November 18-19 Philatelic Collector's Series auction in New York.
The lot is one of the most important covers from British North America (BNA), the name given to those regions of Canada under British rule.
It was sent from Nova Scotia to Madras, India in 1853. The envelope is a petit mourning cover, with the black border indicating it contains condolences for the deceased.
The sale's emphasis is heavily on Canadian stamps, with a Newfoundland 1857 2d scarlet vermillion cover valued at $10,000-15,000.
It displays a horizontal pair on an envelope bound for East Boston in 1859.
Spink describes it as "a lovely and important Two Pence Vermilion cover, of the utmost rarity, as this is one of only two recorded covers bearing this franking, with this being in superior condition".
A block of four 1853 Nova Scotia 1d red brown stamps carries an identical estimate of $10,000-15,000.
It's been housed in a number of high profile collections and features exceptional colours, with large fresh margins.
We have a Newfoundland 1859 cover, bearing an 1857-1864 scarlet vermillion, for sale in our online store.
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