The only stamp of its kind to have an 'NH' grading will star among 40 'finest knowns' in New York
New York auction house Michael I Casper's end of year sale will offer three owners' collections through more than 500 lots, expected to bring $2m.
Particularly impressive is the sale's section devoted to over 40 "finest known" stamps - among which this rarity from 1870 is expected to sell for $50,000.
The stamp in question is an 1870 90c Carmine in mint condition; the only one in the world to have been graded NH - meaning it's never been hinged in a collector's album - by the Professional Stamp Experts (PSE) to date.
Boasting a "deep rich colour, choice centring" for this difficult-to-find issue, the one-of-a-kind piece will be sure to turn philatelists' heads when it goes under the hammer between December 6-7.