World’s Rarest Airmail ?

There are many airmail issues that have been offered or sold as “rare.” Examples include the 1925 25c on 10c “Black Honduras” (only 2 reported, one last sold at auction in 1994 for £104,500); the USA 24c “Inverted Jenny” (though nearly 100 are available, its popularity ensures prices of US$100,000 to US$1,000,000 depending on the centring […]